Mini Starters on a Slant Six

Fitment issues and Clifford headers go together like hockey and beer, eh! It's always been that way. Dutra Duals are a better idea unless we're going racing.

The mini starter swap didn't work for you because the Canadian-built Slant-6 cars kept the starter drive and ring gear dimensions that had been used only in '60-'61 in the States. The Canadian cars had a direct-drive Prestolite ("Auto-Lite") starter similar to the US '60-'61 Slant-6 starters.

The gear-reduction starter, first used in '62 on everything in the US and on V8s in Canada, introduced a new starter drive/ring gear geometry. The drive pinion has ten teeth and is ø32.5mm (vs the '60-'61 US and -'66 Canada, with 9 teeth and ø25.4mm).

There is no parts store off-the-shelf starter that will directly replace the early-type \6 starter. If you want to run a mini starter, you'd either need to custom-build one or swap in a torque converter or flywheel (as applicable) with the later ring gear on it, then you can use the same mini starters you read about other people using, including the '91 318 item you bought.