Which Starter Bolts Do I Need?

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I have a 1968 C-10 with a manual trans, and a small block engine. The starter has a cast iron nose, and the mounting bolts go thru the nose, into the bellhousing, and NOT the block.
My question is, where can I find the correct bolts, as each of them is different. The bottom one will have a large shoulder, the middle one has a smaller shoulder, and the top, that bolts thru the bellhousing, into the starter, may not have any shoulder!
I have NO bolts right now, had my local dealer look, they even called the factory, and nothing came out!

I want to keep the starter that I have it's new, and I don't have any block mount starters right now!
The hole for the bottom bolt is almost 7/16". Is there a bushing for this?
Thanks,