Turtle
Check out mounts for 60 - 66 Chevy with small block but watch for different frames some trucks had tortion bars etc. I'm not sure if GMC and Chevy is the same frame but my 65 GMC ( factory V6 Power Glide ) has 65 Chevy truck 283 with 68 Chevelle Power Glide. The rear mounts look factory and it looks as if the front mounts were slid back on the frame and new holes drilled .