1986 GMC sierra motor mounts not lining up.

I am putting a crate motor in my truck and cleaning up the engine bay and painting etc. The old motor mounts were shot they were crumbling. So I bought these off of classic industries 1986 GM Truck Parts | T83099 | 1972-96 L6 & 8 Cylinder Frame Mounted Motor Mount | Classic Industries .
Found out that they are the wrong mounts. They have have the mounting holes but the entire mount is 1/4 too short and so are the mounting holes. So I went to autozone and asked them to show me some mounts for my truck and guess what? They bring me the exact same mount with the same chinese stamping number on them. So instead we looked for other mounts a few yerars before 86 and after. He found some mounts for a 1987 that were identical to mine. However the center hole diameter is not the same. My mount clamshells center pin hole is 1/2 diameter and so were the new wrong mounts. The center pin hole on the 87 mounts are 7/16. What am I supposed to do? The clamshells were a direct fit on my crate engine...

Welcome to CHR!
If I understand your explanation right, it seems to me you could either drill out the 7/16" hole to 1/2", or buy a couple of new 7/16" bolts, nuts & washers in Grade 8 to fit.