The "add a motor to manual window regulators" kits from (many

) years ago, when I was in automotive aftermarket, just barely worked, before they invariably broke or failed.
Having said that, I simply don't know if any of the current kits are any better. Maybe someone with one, or has tried one, will chime in.
Honestly, *if it were me* on a '96 truck, or anything post-1995 with GEM controlled windows, I'd look at replacing the manual regulators w/ cranks, with OEM power regulators w/ OEM motors. Then I'd not worry about the GEM, and just wire the new power window motors to a pair of DPDT switches (such as earlier OEM switches).
For driver's window auto down, the OEM setup through '94 was a small module added inline in the driver's door to the motor's down wire. I'd go this route.
Another consideration, is that to repair the power window system down the road, dealing with aftermarket parts is a huge pain the ass, usually not being available anywhere. By using OEM parts to build a simpler power window system, your replacement parts situation will very likely be much easier.
You'd basically just be building an OEM pre-GEM power window system into a later truck that changed in '95 to using a GEM for the windows.