I had my cab off and on about 6 times, (which is very hard on paint) and it seemed like the dash area may have been what was hitting the inside of the body. I lowered the dash but, it did not help. I then trimmed the front outside edges of the interior but, that did not help either. I have heard that the window cause the fit problem but, it was not clear to me. I have one more F350 to build and I am going to do a lot of trial fit before I paint anything.
I like your work so far Ghoodii I can't wait to see the finished product!