Hello Mark, A few years ago I had a similar problem with the assembly of the Revell 1960 Chevy. I eventually discovered a conflict between the windshield glass and the door panels. There was a cut-out on the front of each door panel that was supposed to accommodate corner of the windshield. The windshield, however was too thick for the space allowed preventing the interior from sliding up far enough into the body.
I tried a number of adjustments and modifications before I discovered this issue. Here's a photo of the problem and a link to the build page.
Same company, similar models, there may be a similar problem.
Hope this helps,
David G.