All those numbers are for 6 volt systems, and short cap distributors. It appears that there was a cam design change with the switch to 12 volts and the tall cap and rotor. I just wanted to make the point that "39 degrees is too much dwell" might not be an accurate statement. I'll do a little more research on the later model distributors- - - -I think I've got some later model specifications stashed away somewhere.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!