I can confirm the difficulty of replacing a starter with engine in. Man is that a hard job. Well, now that I removed the old one, which is being replaced because the electrical terminal has shorted out and is loose, I struggle to install the new one. That bottom bolt takes some effort. Anyway, trying to start it, did I mention I was replacing an accelerator cable and had to remove the seats and floors, anyway the starter is grinding badly on the flywheel when I crank. No, it can't be, I have to take that damn thing back out again. OK, so I got it out and started to compare old and new. This is where the interesting part is. They are indeed different, although they appear the same, the new one has the drive about 1/8 inch closer to the body in the relaxed position. Now I can see that there is a difference. I got this 16121 from Autozone and ordered it for a 1300cc 1967 Spit, I think. They are all the same so I thought. Since this has to go back, what did I do with that receipt, I wanted to know if anyone else has ever heard of this problem, and what the sure application is to get the right one. I will post the resolution to this after I find out what went wrong.