Or another option would be to run a fuel pressure regulator with a return port, and route the return from the regulator thru the OEM return line.....

As for the mounts, did one of these years ago and just used the mounts out of a G body Monte, welded the frame mounts to the crossmember and used the stock Monte motor mounts on the engine. Just install the engine with both frame and engine mounts bolted on the engine and trans bolted on the engine, set it in the chassis straight and level with the trans bolted to the crossmember then weld or bolt the frame mounts to the crossmember.