STEVE - OTB, "Old Three Bottom" posted video of the new 12v alternator he just put on his "War Baby H", about a '41 or '42. Engine spins over like there's no plugs, starts right up and purrs, charges at 30A. You'll never get a 6V Genny H or M to do that!
There's a few old timers on RPM that still resist 12V and alternators, but fewer every couple months when the topic comes up.
The diehards all claim big battery cables, clean grounds and a charged fresh 6V battery are key. Dad's '51 M was delivered December 24,1951, and wouldn't start the first time on Dec. 25,1951 at zero degrees. New everything, about ten days out of FARMALL. And the 4" M&W pistons, M&W live hyd, and Char-Lynn P/S just add drag or resistance to it's ability to start. On 12V it starts on about the third revolution after setting for MONTHS!