Will 1993 Chevy cab fit a 1986 truck frame?

No, a 1993 Chevy truck cab will almost certainly not fit a 1986 Chevy truck frame without significant and likely impractical modifications. While both are Chevy trucks, the body styles and frame dimensions changed considerably between 1986 and 1993. The cab mounts, firewall location, and overall frame dimensions are different enough to make it a very difficult, if not impossible, project.