What to do?

[69 blue coupe]

I've got a 1972 swb I've recently purchased,it been sitting in a garage for the last five years with no engine or trans. But it did come with Dakota digital dash ,Dakota digital controllers for airbags,train horns,power windows, owner removed airbags but gave me the parts with the truck.ok at first my plan was to clean the engine bay put in a l92/6l80 truck engine,tsp vvt4 cam,stall,and put air ride back on buff paint and that was going to be it, so I get the truck home look over some more and stat to find rust some on fire wall and where the cab mount to frame also after looking at the truck I don't like the paint the green and white is the original color and It'll look better than the green and gray.my ? Is with this frame mount problem should I do a frame off or should I have it fixed and paint the truck and frame with out removing the cab?