we are doing the exact same thing with our 70 fastback. Here is the info i have.
390 block
CJ 428 heads ( we are going with aluminum repro's from Summit)
428 crank, rods, pistons, rings (all in one kit from PAW)
as far as the toploader, we are trying to find one too...sorry.
if you have any other questions, i'll see what i can answer.