The GMC motor is 1 1/2 longer than Chevy.
Look at the frame mounts to if some has done something to the frame mounts ?
Chevy front cross member is not the same as gmc.
Look at the radiator mount to see if someone put a GMC clip on a Chevy?
If you post a pic of the radiator mount from the front under the valance I maybe able to tell you.
Most of the GMC's had a u bolt style mount.
