Chevy Duty (and probably the other suppliers, as well) carries a replacement bracket for a dual-master upgrade. On the AD pickups, the bracket is very simple, and I know some of the guys on this site have made their own.

I believe the consensus on the best MC donor is a '69 Mustang, with the biggest plus being that the residuals are built-in.

Chevy Duty's bracket is in the neighborhood of $100, and I think allows for a mid-70s Chevy sedan MC to bolt on. Not sure if the 'Stang MC will fit on it or not.

Ed