im puttin a LS1 in my jeep, and would like to know if i can use the 6speed trans from the LS1 and if i do what i would need to do to use a atlis tcase...i dont know if you want to call this hardcore or not but i see people asking about flopping your jeep in hardcore so i thought this would be ok to ask

I think that was the same tranny I was looking at and if it is a t56 then no one makes an adapter. Easier to go to an auto.

Even if you could find an adapter, I don't think it'd make for a great offroad manual with it's gear ratios, unless you're planning on making some kind of tribute jeep to the guys from the 70s that ran obstacle courses.

info from http://www.gulfgt.com/forum/showthread.php?t=11038 (shows pic of trans, too)

TREMEC T56 (MM6 / M12)
MM6: T56-1386-000-22
M12: T56-1386-000-25

Maximum engine torque: 350lb-ft/474Nm (MM6) 385/522 (M12)
Ratios:MM6....................M12
1st:....2.66...................2.97
2nd:...1.78.................. 2.07
3rd:....1.30...................1.43
4th:....1.00...................1.00
5th:....0.74...................0.84
6th:....0.50...................0.57
Rev:....2.9....................2.9
Gross Vehicle Weight: 4000 lb ( 1680 kg )
Case material: Aluminium
Center Distance: 85 mm
Fluid Type: Dexron III
Transmission Weight: Wet: 54.9 kg
Fluid capacity (approximate): Dry 3.8L
Power take off: No

GM NV4500 Will bolt to it and they make adapters for that. If you don't want to go atlas you could go sm465 and np205. I am in the process of putting the LS1 sm465 np205 into a scrambler. So far so good. Just dont have enough time to work on it.

i just dont want to use the stock jeep trans cas i dont belive it will hold up..and also my stock tcase wont hold up either i have a heavy foot, so i would need a nv4500 and i think the 205 is too big and heavy so i would rather have a atlas

A 4L60 is a good auto, low first and a decent OD if you want an auto (I been told), otherwise a nv4500 is your best bet. Atlas is much better than a 205.

I dont believe you can get an adapter for the t56, look for a new manual trans from a 3/4-1ton, those should work

so like a GM nv4500

What is your plan for the jeep
wheeling or road use DD?
If its heading toward wheeling rig only no long highway trips
save yourself and go to a TH400 it will handle the power and abuse.
Forget about a stick- just a waste of time and money.
You may want to look around over in the gen4x4 section for information
on your drivetrain questions.