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.
It looks like you boxed the frame rails, but the x - member still appears to be original. I really don't know if it's necessary to box that part, but just in case - we have just finished doing that today. I am sure that 3/16" plate is more than enough to prevent the trouble my frame went through. It was actually frightening.
Thanks for the info on the wood. I guess maybe that must be stock then, because the angled portion of the firewall on mine is wood, and that extends also back to the front seats as did yours. And there's not even sheet metal covering it. Not sure what we will do about that, but it will either get covered with sheet metal, or removed and made from scratch from sheet metal.
I'm afraid I have no experience with body work, so widening my rear fenders is likely out of the question. Our solution was to narrow the back several feet of the frame, which will also mean we will need to narrow the rear end. That will give us room for the new rear wheels and tires, two different ones of which we are considering at the moment. I wish I had 1/10th of your bodywork skills.
I think your sedan is unchopped right? Could I prevail on your good self to let me know what the height of both the front and back windows are please? That way I should be able to find out how much it has been chopped. Thank you in advance.
