The internals are not the same for car and truck.
The main difference is the counter shaft in a car trans uses a bushing and the truck needle bearing so they will not interchange. The rear bushing and housing are different as well. The gear ratios are different so most of the gears will not work. I think the syncro slider will interchange but not positive.
I have several good truck 3 speeds and have in the past gutted a trans and shipped just the internals in a flat rate USPS box. If your stuck for parts let me know and I'll check out what I have.
