The 2.5 4cyl & 2.8 60deg V6 have a much smaller/narrower bellhousing bolt pattern. They also put out much less HP so they can make do with smaller trans compenents such as smaller input shaft. They can be modified to work with a 235. Well, I know the 2.8 T5 can. They also have different gear ratios. The T5 from a 4.3 90deg V6 (same bellhousing pattern as V8) is a stronger trans with the common input shaft.
My friend verified the 5spd I used in an S-10 was indeed integral. I should be out there tomorrow, so I will get numbers & pictures.
