Do not know if GMC and Chevrolet used the same assembly and if so if there were any significant changes from ‘36 to the later years. I do know the later years Chevy trucks used a spring to address the drooping issue. As for the latch assembly movement, my suspicion is the assembly is gummed up and needs to be removed to clean years of accumulated gunk. Slamming the door will likely eventually lead to otherwise avoidable damage or breakage.
Attached is a photo showing a latch assembly for a ‘46 Chevy 1/2 ton. The assembly on top replaced the one shown on bottom.
Last edited by 46Sparky; 04/13/202612:07 AM. Reason: Added photo explanation