I know that camaro/nova subframes will fit in the 47-55 AD trucks. The 42 will probably have different dimensions. It might be worth measuring one to see if the width is close. Another thought would be an S-10 frame.
I know the thought of putting ford parts in a chevy is horrible to some, but the the mustang II styled front ends will probably be the cleanest approach to get a good ride and decent handling. Most of the aftermarket front ends are based on the mustang II design but hardly use any ford parts. Take a look at fatman or tci suspension setups.
