We did one in a 65 Coronet a number of years ago. Used a motor plate, centerline in the stock location as far as side to side. Moved it back as far as possible without modifying the firewall. Maybe lowered it a touch. We had to "slice" the right shock tower to clear the valve cover. Did a nice straight cut, welded a flat piece back in and cleaned it up. He wanted it period correct, but I couldn't bring myself to do the BFH mod. IIRC, we moved it about as far as we could without getting too close to the shock and we still had to loosen the top of the shock to get the VC off. Wish I had pictures.

I had a plastic long block to use, but didn't trust it. Was flimsy. Clearances were so close I used a real block to avoid any "oh $%!^s" when it was put together.