Napco 4x4. Check this site out. Lots fo good information on Napco and other early GM 4x4s, plus there's a classified section that does have several complete and parts Napco trucks listed.
To add to what bartamos said, going late model will be easienst as far as aquiring parts, but the late model axles will be wider that the Napco axles. Plus there will be some fabrication involved to adapt the steering box and a mount for the 'case.
