The Pontiac engines in GMC's used a single front mount,similar to the early 60's Chevy V-8's in the one ton and bigger trucks,only it didn't fasten to the block,but rather it attached to two ears that were located on each side at the bottom of the timing cover. When I installed the 1968 400 in my '57,the same mount fit my new engine,making that part a bolt in. The rear of the engine used an iron bellhousing with mounts,also similar to the Chevy V-8 set up,only with the early Pontiac block pattern,which changed to the BOP pattern in '64. I was unable to find an iron bellhousing with the mounts and the later block pattern,so I made a plate to fit the original mounts and fit between the bellhousing and the transmission,and I used a standard aluminum Pontiac manual bellhousing;not the strongest set up,but I haven't broken it yet,and I've given it reason to break.
