I don't know why Mancini and others say one mini-starter is for a big block, the other small block, maybe they think people are that stupid? I am a small block person myself, and I just went and got one at O'Reillys..before I put it in, My buddy told me he ordered the "Big Block" one from Mancini and asked if i could help install it(He's not so much mechanically inclined)

I go over there and thought I'd take mine along for comparison, I knew you had to grind away a SB starter to fit and I wanted to see what was different.

The body was the exact same on the Mancini "Big Block" and my O'Reilly factory unit. I ground away at different spots where it snugs against that boss on the block as carefully as I could for about 2 hours. Each little bit I buzzed it and check fit, buzz, check fit.. I didn't want to get carried away. I made sure that i had a slight bit of play in the unattached starter before i bolted it in. So I wouldn't bind it.

If you guys who have your BB motors out want to use one of these things, My suggestion is take a little off the block in that looked nook. Some have more there than others. It'd just be better than grinding on starters that you may not be able to get a core exchange on.