I used a purr power muffler designed for the G62 in mine. It used the old Byron mounting scheme but I added a firewall for the G62 mounting. I didn't like relying on the Byron mounting scheme by itself. You should be able to fit a G62 with a wrap around style muffler without any problem. You will need a new fire wall to mount the G62 or any other engine. At 25 lbs the G62 will be plenty of power for the mustang. A 3W75 (2 blade prop) would be a little bit of overkill unless you like extremely fast warbirds. I had to add nose weight (2 lbs) to mine but I have my elevator servos in the back and most of my radio gear is more aft than usual because I have a full cockpit and pilot. You may find that with a G-62 up front you will balance okay.