A second test of the cables, this time using an ESR meter capable of
measuring hundredths of ohms and able to null test lead resistance.

(-) battery cable, from battery terminal to chassis: 0.02 ohms;
(+) battery cable, from battery terminal to starter solenoid: 0.05 ohms;
Alternator cable, from alternator to starter solenoid: 0.33 ohms.

These measurements were done with (-) cable disconnected from battery post
(no potential across cables) and test leads nulled.

So 35 amps charging current over 0.33 ohms pretty much drops the full 12
volts.

I'll look into wiring and terminal issues.

Thanks to all who helped.