[32phil]

The first thing to do is to check to make sure the body/subrails are in the correct location to each other. If not they must be corrected first.
I have dealt with several 32 original frame/bodies that have had this problem.
In all cases the problem is caused by the rear frame horns have been bent down due to a rear end collision. I had one that was only bent down on the driver's side with the right side being bent down only slightly.
At the center of the rear panel, you should have about 3/8" gap between the top of the gas tank and the bottom of the rear panel. Make sure the body is bolted down and shimmed properly and the gas tank is shimmed properly as well.
Look for tell-tale bulges on the side of the rails at the kick up This is evidence of the rails being forced down. The rails should be perfectly flat along the side at the kick up.