Well, I own a Mk1 Capri and fitted few years ago an Rover 3.5 V8 engine along with 5-speed transmission and you must at least raise the transmission tunnel about 4-5 inches. Also the propshaft will be too short so you'll need about 6 inches longer. I can't remember all the modifications but it'll be quite lot of work!
I can't weld myself, but both my friend and I have many friends who can help us out, btw, there are still a few interior bits availible, mainly the door panels, but the seats and a few bits of trim are gone (Thanks Jamie).