mini starters for a 1966 273 header install

You don't have to shell out mountains of cash for any of the massively overpriced mini starters marketed as custom, "rare" custom problem-solver items. The most compact, block-huggingest starter to suit the application is the stock starter for a 2005-2008 Dodge Ram pickup with 5.7-litre V8 engine and manual transmission (automatic is totally different, will not work). That's this one. It is a coaxial starter—the motor axis is the same as the drive axis—which makes it more compact than the regular mini starters sold (at stupid markup) through MP and by other vendors; those are offset starters (motor axis outboard of drive axis). Pic here and here of this starter on a Slant-6; look how closely it hugs the block.

Unlike the other starters, this one has one of its two mount holes threaded. Drill out the threads so both holes are plain. On the 6-cylinder applications there's an engine-to-bellhousing bolt that interferes with the mount pad of this starter; that problem is easily fixed this way—I don't think you'll hit that problem in the V8 application.

(Don't forget to charge yourself a lot of money for drilling the threads out of that one mounting hole, thus making the starter into a special, custom, "rare", expensive item!)