Sounds like you've got it covered. I think I'd try the resistor in the pull-in winding circuit first- - - -it might save you the cost of buying a 12V solenoid. The only time the heavy current is an issue will be the fraction of a second when the pull in winding is engaging the starter drive. Once the gear is engaged and the armature is turning, the heavy winding is disabled, (same voltage on both ends of the pull-in coil) and a MUCH lower current winding keeps the gear in mesh. That's a really good engineering feature that was built into GM solenoids.
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!
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