I’d like to add my thanks to the responses to this post. I’m at the point of replacing the full quarters on both sides of my 65 Dart coupe. Yesterday I finally got the trunk surround, including the lower rear window frame, from my donor car welded on. I was thinking of putting it on my rotisserie to do the quarters, but wasn’t sure if I should. Now I definitely will wait until I have the quarters on. After replacing the floor pans I welded a cross brace across to each door jamb with a triangular “V” attached to the top of the driveshaft hump. I also used braces from the hinge mounts to the latch to keep things square that way. So far, so good. When I replaced a section of the driver’s side rear sub-frame I made jigs that ran between each spring perch, making sure that the center-to-center distance matched the specs on my factory frame chart. Interestingly enough, the passenger’s side perch was 3/16” short from the factory. Thanks again for the informative responses. I’m not a body guy, so I’m always glad for any help I can get.