89 is tbi and the 96 is a mpi magnum engine.
myself I would use the magnum engine on the 89 trans
89 wire harness--wire in a VR on firewall, by-pass the in-tank FP relay to get stock pump to run, add a fuel regulator on firewall, use edelbrock/magnum intake/carb, bypass dist to run a points dist converted with a pertronix unit. (or any 12 volt stand alone system)
done a couple 89 pre-magnum engines this way with good results. those roller cams respond well to the carb/intake swap. same for the magnums when used in the 86-91 trucks
I run a whiplash roller cam in my 91 pre-mag 318 with holley street dom intake/q-jet.
but that's me with no $ building junk..lol!