What I have is a 1977 chevy 400 small block/SM465 tranny and currently it is set up with stock intake and quad carb.

I have a 1990 k5 blazer 4x4 with a 350 TBI/Auto 4speed that develped a knock, (Pulled engine on sat and #1 rod bearing toast). Found a donor Chevy van complete. I plan on pulling the van 350 and putting it into my blazer, which leaves me with a good set of heads/intake (old TBI blazer engine) and all of the TBI stuff off the van, perfect for my v8 swap in my cruiser.

What do I have to do to the 400 for the TBI to work?

I know I need to remove fuel pump from block and get a blockoffplate. Also I know the wiring harness/sensors and new fuel pump need to be used for running reasons....

Main issues are....
Can I use the stock heads, or should I bolt on the 350 heads (for intake issues? (heard that 87 intakes don't bolt up to per 86 heads, correct?)

Any special head gaskets if I go with 350 heads on a 400?, i.e. thickness of the gasket

Camshaft, is the camshaft basically the same or is there a big diff between the older carb/ TBI vehicles, i.e. mainly 350's

Thanks

For the heads you will either need to drill the steam holes in the 350 heads, (Use a 400 Head Gasket as the Template) or elongate the center bolts in the TBI intake. They are the ones on either side of the heat crossover. The gaskets should work either way. I'm not sure on the cam. But, I would bet that it is in the ballpark.

I am thinking about this exact swap in my 87 Blazer...

Yes, steam holes will be needed. 86 and prior heads are different the 87 and up heads... vortec heads also take a 3rd type intake. You can get all 3 types that will work with your TBI.

One big issue is air flow and fuel. The stock tbi and injectors won't keep up. Some dealers have been advertising TBI 383's that are fragg'n cause they run way too lean. I would get a Holley upgraded unit. You have a few different injector choices and then it will flow about 700 cfm. You also will get to play with the fuel pressure to tune it some, but you may need a custom chip burned to get it running right. Cam wise you are kinda SOL. The entire TBI ecm runs off of Vaccum for the most part, so your cam choice is extremely limted without ecm chip help. Your bestr bet is to contact some cam manufactures about computer cams.