Most Jeeps use a transfer case to get 4WD, so there should be little difference in converting 2WD vs 4WD...
My AWD RAV4 uses a transaxle with a transverse mounted engine (ie side-ways) - this greatly limited the size of motor I could use (a 9" Warp just barely fit).
Hopefully your Jeep is not transverse, so you should have lots of room to put in as big as you want.
A quick search for Jeeps in evalbum.com showed at least 12 conversions - I would start there to see what others have done...
My AWD RAV4 uses a transaxle with a transverse mounted engine (ie side-ways) - this greatly limited the size of motor I could use (a 9" Warp just barely fit).
Hopefully your Jeep is not transverse, so you should have lots of room to put in as big as you want.
A quick search for Jeeps in evalbum.com showed at least 12 conversions - I would start there to see what others have done...