Will a 99 Chevy truck cab fit on an 85 frame?
No, a 1999 Chevy truck cab will not fit on a 1985 Chevy truck frame. The frames are significantly different in size and mounting points. The body mounts, cab mounts, and overall dimensions are incompatible. You'd need a significant amount of custom fabrication to even attempt it, and it would likely not be a safe or practical project.