Small block mini starter
Put a starter from a 90's RAM truck in my 273, cost ~$10 at JY including the cables (which I used). I also got 2 rebuilt ones off ebay for ~$45 to use on my other 60's Mopars when needed. I don't recall any problems bolting it in. Indeed, it was much easier than was getting the original beast out, which barely fit past the exhaust and steering gear, with the wheels turned just so.
The mini-starter seems to turn the engine over faster. It fires in ~1 sec even with a carburetor. It seems to make a higher-pitched whine, sounding like a little turbine engine.
Up on ramps this weekend, I noticed it looks like the inner tie rod on the driver's side might brush the thin bolt on the starter, or at least the cotter pin does. I'll check closer. Seems like the steering was catching slightly when I drove it the first and only time.