I've thought about this too but the manual trans has the biggest issues. The manual shift linkages on a van are complex and it would take some serious redesigning to make it work (anyone want to take a crack at electronic shift solenoids and a control module to rig one up?) Auto 'might' work but the extension housings on either trans won't. The engine and transmission are set way back compared to a truck drivetrain. The innards of the transmissions are the same AFAIK.