I've I'm... Had a few of these transmission.
There is several differences between the two. Most would not stop you from using a 97 and down version. The most noticeable differences between the cases are the cooler line location. Other differences are inside the case, shafts, solinoid changes, planets, sprays, lube Circuit, bla bla. Most people seem to feel the later ones are superior . There is also a tail shaft difference as well, ill add more this below.
If I were you, I would get a 99 and up trans, It has the bolt for the 12 o'clock position. It also assures you get the correct shift modul and plug style although most trans shops selling a trans will not have this included as it would not come in with their cores.
Stock remains around here are 895 ish, the only upgrades for a stocker I would ask for : upgraded boost valve, transgo stage 2 shift kit, a rear anti walk bushing at a minimum. if your feeling fancy add a in pan trans gauge and lubeseal reusable gasket. the return lines on these stock also use stupid clips, and the threaded in adaptors are different from one another and earlier year trans. There a linking build thread on the last few pages to a source that sells adaptors to put the lines to AN -6 .
If I were you I would try to find the 99 and up trans for a core/ new unit. then use a pass drop 241with 32 spline with a vss set up. You will also want the adapter.
The stock truck set up would have had a 4x4 control modual, this is a whole separate pile of crap/wires/box in the cab ect. If deals with when the truck is in 4 low. If you are starting fresh I would ask him to delete any of that from your tune or hopefully your tune is for a 2 wd truck with this not as a factor.
You may need to extend your vss wiring if so, no biggie. Your vss plug may not be correct for you t-case sensor if so gm sells the one for all of the t cases, it was around 20 bucks. Just go in with what ever year t case and vehicle you got the t-case from.
If you have not already got motor mount adaptor brackets btw several people sell them online, uses your current motor mount style and is a 3/8 plate that outs the motor where it should be as the block has th bolts a few inches off from your current motor.
Russel also makes the line adapters that will clip right on the factory fuel rail on the motor. These motors also had rail that had returns and other years that had a returnless system that was regulated at the pump assembly. postk up what you have.
Summit sells adaptors for sending units to use your stock gauges as well.m,
I'm rambling, I'm tires are hell too nd this ipad is killing my typing,m But post upon you have questions, plenty here have already done this swap.
-shane
