I purchased a distributor gear from summit racing part # 10456413 for my crate 454 gen vi motor. I am using a mercruiser thunderbolt V distributor. When I tried to install it, the holes don't seem to line up. The old gear had 2 sets of holes, as pair closer to the actual gear and then another pair a little further away. The old setup also had a shim washer or thrust washer between the gear and the dristributor body. I'm not sure what to do? Should I be using a different gear? Should I remove (this doesn't seem like a good idea) the washer? Any help would be appreciated! Here is a pic of the new gear next to the old gear, the old one is on the left.

I had the same isue with a new cam and dist gear setup.

He have some diferrent shim thickness size to get the right shaft end play.
But on my dist gear i do a machine work to reduce the thickness of the gear a litle and readjust with Moroso dist shim kit.

You need the good shaft diameter shim kit and you need to run them with one shim no more.

Hope that's help.

The new gear looks like it came from China. Is that a roller or flat tappet motor, you may need to run something different if it's a billet cam.

Yea is a hydraulic roller came. Came stock with the crate engine.

Go to any Chevy dealer and purchase a melonized gear. They run about $85. Mine even had them in stock.

But this is the ACDelco part that GM recommended for their crate motors. Is my Chevy dealer going to gvie me a different part? I'm not sure what I should do next?

How many hours are on that gear?

I don't know how many hours are on the gear. It came off the engine that came with my boat. It had spun bearings. The other gear is brand new. Anyway I measured the shaft in my distributor next to another thunderbolt distributor shaft and they are the same lengths. The only difference is the hole for the gear. The one I compared it to had the hole 1/16 further down the shaft. So it looks like the last engine builder drilled the gear to fit the messed up shaft. I'm doing the same. It's at a machine shop now.