You should be able to just do a swap from the 1995 to 1996 4L60E transmission. here is a little history on the 4L60E.
Before the Late 4L60-E transmission, there was the Turbo 700R, which was introduced in 1982. The 4L60-E is GM's successful continuation of the ever-improving 700R4 (aka "4L60" since 1990), introduced in 1982. The 4L60-E is the "E"electronically shift controlled version of the 4L60. The Late 4L60-E was released in 1997 in and fully phased into wide use through GM by 1998 in both RWD car platforms (including the C6 Corvette) and trucks in both 2wd and 4wd configurations.
Mechanically, the transmission's power transmitting core remained the same as its predecessor, but the valve body and actuation system for the clutches, bands, etc. is controlled by electronic actuators and solenoids. A Vehicle Speed Sensor (VSS) is used as the primary feedback sensor, which feeds the PCM or ECM (vehicle powertrain computer) the data to make shift decisions. The engineering of this system is not regarded as a complication, but an elegant simplification and further improvement to this transmission.
The 4L60-E derives its designation from its specifications: 4-speeds, Longitudinally positioned, 6000 lbs. GVW, Electronically controlled, although the transmission sees factory service in trucks up to 8600 lbs.
The strength of the 4L60-E has turned out to be remarkable. Now a darling of the transmission building aftermarket, the 4L60-E is capable of transmitting impressive power from both truck and performance car applications.
Identification
The Late 4L60-E transmission has a three piece case of cast aluminum alloy; bell housing, main case, and tail housing. GM shortened the package to 21.9" long - equivalent to a manual transmission of 15.4".
The input shaft has 30 splines. The transmission typically has pinned flare & o-ring fittings on the passenger side for a cooling circuit. The transmission has a square oil pan.
The key distinction of the Later 4L60-E (1997-2006) from the Early 4L60-E (1992-1997) or 4L60 (1990-1992) or 700R4 (1982-1989) is the six-bolt "hex" rear output or tail housing / adapter pattern. The previous versions featured a four-bolt square bolt pattern at the adapter or tail housing. Additionally, the removable bell housing is also another distinguishing feature.
Two-wheel-drive versions have tail housings and typically a longer output shafts than four-wheel-drive versions, which have various adapter assemblies and a shorter output shaft.
The transmission weighs 146 pounds dry, and 162 wet. It requires 8.4 quarts (9.64" torque converter) or 11.4 quarts (11.81" torque converter) of Dextron III fluid, which the factory claims to be a lifetime fill. Deep pan versions require as much as 14 quarts. Length and volume of the cooling circuit will vary and will require an additional amount.
The 4L60-E is found in nearly every GM rear-wheel-drive application, including the C/K Truck, Sonoma, Jimmy, Tahoe, Yukon, Astro, Safari, Suburban, Bravada, Firebird, Camaro and Corvette.
Hope this helps, just make sure you do the upgrades to the transmission like replacing the servo's with the Corvette servo's and the boost valve with a 0.490" size to ensure you have proper transmission line pressure. Test the transmission by putting a line pressure gauge (or visit a local trans shop) on the pressure test port and go for a drive to verify proper line pressure. Base pressure at idle in P,N,OD should be around 70psi and around 140psi in R. Max line pressure should be at least 190psi at WOT in 1st or 2nd, 225psi is optimum. If base pressure is low, trans or pump is worn out. If max pressure is low, check EPC solenoid. If reverse is slow to engage, and line pressure does not come up to at least 130psi in reverse, replace the boost valve with a Transgo 0.500" boost valve or 0.490" (easy fix in pan). I found the 0.500" boost valve to be to firm for my jimmy buy might be OK for your heavier truck.
