Couple of suggestions for you.
1st, the 12/24v cummins has been swapped into a wide variety of things and most of those are well documented on-line. Spend a lot of time searching.
2nd, unless you have an emotional attachment to the truck, sell/part it and start with one that is closer to your wants already. You will be money and time ahead, especially since the truck you would be starting with is a rust bucket.

 

F100's could come with factory 460's??? That seems odd...

I don't have experience with a 6BT in a '70's model Ford, but I am intimately familiar with both in their own regard. The 6BT is tall...very tall...and the industrial pan just makes them taller (the industrial pan is deeper than the Dodge pan everywhere). Is your 6BT front sump or rear? The pan will mount either way, but you'll want rear sump configuration for your F-100, thus you may have to source a Dodge pickup tube if yours is front sump. The crossmember is pretty high and forward in the F-series, but could possibly be avoided with a Dodge pan and body lift. You may have to clearance the crossmember a little. I would not go through the trouble of splicing a frame. Worst case, find a similar year model F250/350 frame and swap it in for marginally improved beef at best and factory front leaf springs (assuming 4x4 frame). A Dana 60 front axle will be the best bet, and I'd look at Dana 70/80, 14 bolt or Sterling 10.25 rears for adequate tow pig beefiness. Or, if you keep coils, pick up a set of Super Duty axles (D60, Sterling 10.5, metric) and enjoy beef, better turning radius and smoother ride at the expense of having to get metric wheels. Depending on which transmission you run with (I'm assuming the F7000 probably has a large Eaton or Allison) you may have to resort to body lift of doghouse modification. A divorced NP205 would be easiest for 4x4 in either case, unless it's an Allison 1000...but then it gets pricy reconfiguring to 4x4 tailshaft and such if you want to go married t-case. I've seen some home brew tails for putting married NP205's to Eatons, but it looks like a lot of work for little gained.

There's plenty more to learn on the matter, but it can be done with minimal fabrication if you do your homework and gather the right parts. Good luck!

 

An old F100 frame is probably not the best starting point for a heavy engine in a tow rig. My ''79 Bronco frame was paper thin from rust in the whole back-half.

I would look for the heavier gauge F250/350 frame w/cab (for prototype/fitting) and build that. Then do a body swap at the end.

EDIT: The F100 weight tags could be a problem.

 

Keep the F-7000 frame,just shorten it and swap the cab and bed add one ton running gear....$.02

 

Great thoughts. I was searching around last night and found a rig where the guy swapped the body on the F7000. From what I am gathering, I am close but in reality the two trucks components don't go together like ham and eggs, like i originally thought. Ill post some pictures tomorrow of the two trucks and get specifics on all the components. I have 2 young kids so loading them up in either truck is a no go, but in 3 years they will both be legal without safety seats, just regular belts.

My end goal is to build a pickup DD that can tow my farm tractor too and from my farm to various hunting leases, and retire my 4runner to offroad duty. Figured my cummins was to nice to waste. I cant afford a new F-250, and I want a one off rig, figured a cummins swap was the coolest thing around. Ill get some pics gathered on what i do have and forge a path from there. Everything Im reading tells me the F100 just isn't the right truck to put the motor in. I have found that most recomend getting a dana 80 rear and dana 60 front axle and the NP205 t-case, so the hunt begins for those parts, or a donor with those parts. I think the advice i get from the posted pics will point me in a better direction. Thanks for the responses!

 

I'm just puzzled that a 4x4 truck of the same make could be used to convert a 2wd. The internet is amazing that way. Never know what you'll learn next.

 

use the 2wd frame and just hang an axle underneath it. Thats what im doing on my truck. 77 f250 2wd with a 12v and 05+ super duty axle, front suspension and steering. Using 1st gen dodge (cummins) motor mount brackets and prothane jeep motor mounts the motor bolts in with just drilling 4 holes. If you keep the truck 2wd you would have to notch the oil pan to clear the steering linkage.

 

The F-100 frame is formed from much thinner steel,I would not feel comfortable with a 6BT in it without considerable reinforcement...$.02

 

Concerning the F100 frame, The frame should handle the weight of the Cummins…..so long as you don't intend to use this truck to haul or pull anything big and heavy. The factory frame was designed to support about a 1/2 ton capacity with a big block gas engine under the hood. You'll be dropping the heavy 460 for a heavier 6BT, but you'll only be adding about 600 more lbs, which should be well within the frame's capacity.

I would be concerned that the frame was exposed to salt. You said the body has substantial rust, I would suspect that the frame could end up being a lot thinner than original since everything rusts at the same rate under the same exposure. Frames are quite a bit thicker than sheet metal, but it doesn't mean the frame won't rust. They can thin out and still look alright. For that I would consider another frame.

If you're converting to 4x4 anyway, I would use the F700 frame (F7000 ? is there even such a thing?). The frame is a lot beefier and should already have a front leaf spring suspension

….Then again, if you got so much body rust, I probably wouldn't bother using anything from the F100 and just shorten the frame on the F700 and convert it to 4wd. You could sell off the 460 to recoup some of your expenses, but you probably be light years ahead, by turning the F700 into your project truck, since the engine is already in it. And think, with minimal lift, those huge front fenders will clear 42" tires

Ed

 

Back to the weight tags... I wouldn't want to build a truck that had a net weight higher than the GVWR. Best case, '79 F100 2wd pickup has a 5200# GVWR. My W250 CTD weighs 6500# empty.

1973-1979 Ford Truck VIN Tag Codes (Model) - FORDification.net

 

460s are 700ish pounds depending on accessories. In a Lincoln, expect 720, in a race car with aluminum, expect under 550.

Cummins is 1200 lbs. It's a lot of weight but I have zero doubts an F-100 frame could handle it. It's just not going to like the beating you'll put on it compared to the thicker chassis of the F-250+ and that truck will never tow like a larger pickup would.


Personally, I'd just slap some cheap flat tops in the 460 with a straight up timing chain and recurved dizzy, port the exhaust side on the heads, and enjoy your tire burner.

Build the F-700 into a kickass work truck/ hauler. Find a Bronco or an 86-96 F-350 for a wheeler and pull that behind the 700.



An F-700 with Rockwells or whatever the Meritor 4x4 axle up front they came with would be cool as fuck riding on big rubber though. Be fun to get some milsurp tires on it and trim where necessary.

 

A 6bt fits pretty nice in a Ford if you plan it out right, or just sell them both and buy mine :grinpimp:

Cummins Powered Ford F-250 4wd Cowboy Cadillac

 

That is a clean truck, wish my wife didn't need a new car.