The 235 six is about 1 12 inches shorter than the GMC sixes. They used the timing cover mount on the 235 to set the engine in instead of using the correct side mounts for the 235.

Some Canadian GMS may have had the 235 instead of the 270. My bet is they would have used the side mounting holes on the block so the mounts would line up with the holes in the frame.

The 270 GMC six may have had the side mount system too. maybe someone can chime in that knows more about that.