cocobolo, I boxed my complete frame in with about 3/16th inch plate steel. Between the heavy crossmember that comes with the Fatman front end and the upper crossmember I also made and added, my frame is very stiff. I don't ever see it moving in or out. My original lower firewall and directly under the front of the front seat were wood which I done away with. By widening the rear fenders and with the rear end I am using, rear wheel and tire clearance is not an issue.
I also agree that the 33 Ford has nothing on the Plymouth when it comes to looks. Plymouth roofline almost looks like a mild chop from the factory.