I moved the V8 forward exactly 2" in the engine bay on my '65. Since it's a Cadi V8, #1 cylinder is on the other side, so the driver's side firewall had clearance only after I massaged it a little with a hammer. Those 2" made a HUGE difference-spark plugs are easier to get, valve covers and head bolts may all be removed easily. The best part is, there are already holes in the frame, on each side, exactly two inches forward of the transmission mount crossmember. So you can push it forward with a Porto-Power til those holes line up, stick some bolts through and after you measure everything up to make sure it's square, proceed to drill and bolt all the rest of the crossmember holes to their new places on the frame.
I wish I'd done this mod back in the '90s when I first swapped engines. The downside is I had to have a 2" longer front driveshaft made, but the upside is vastly improved access.
For the front mounts, I used the original riveted on frame horn mounts from the small block, modifying them with flat plates to fit the engine mounts of the Cadi. However, if your year came with a 348/409 option, the holes in the frame are already there, you can just move those frame horns around as needed.
The short version of the above, is move it all forward two inches and you'll solve a bunch of clearance problems. Of course, you'll also need to move the transmission shifter and park brake (if it's on the trans) holes. But that's easily done with a sabre saw.
