Question on fitting modern trans in 71 Demon

There are photos of the transmission installed on the 42rh/a500 on the above posts.

I have installed the a500 in my 70 dart with out cutting the floor.You will have to cut the cross member on the upper side even if you do a 2004r.

I have seen both done and i think the a500/a518 would be cheaper and easier than the 2004r.