Anything is Possible!
I once fitted some leather seats (dont know what they were from a mate had them lying around his garage) to my Mk1 escort, I just made up some spacers out of Plywood to get them level(ish) and bolted the whole lot together through the floors with some long bolts and big washers (It never failed an MOT on this, so I am assuming it was ok) the only problem was that you had to move the seat forward to adjust the back rest (not enough room to get your hand between the seat and the door pillar), and anyone wanting to get into the back had to climb over the front seats (they must have been from a four door car) oh and they were a differnet colour from the rears - not much you could do about that!
Cheers
AL