Will a 86 Chevy 4x4 truck frame fit 89 body?

No, a 1986 Chevy 4x4 truck frame will not fit a 1989 Chevy 4x4 truck body directly. While they are both from the same generation of trucks (C/K), there were significant changes between the '86 and '89 model years that affect the frame's dimensions and mounting points. The body mounts, frame crossmembers, and overall frame geometry are different enough to make it incompatible. You'd need extensive modifications, likely beyond practical feasibility, to try and force a fit.