Any 6V regulator can be adjusted to control the generator max output at 35 amps- - - - -just change the spring tension on the current regulator. Just be sure the generator is wound to produce that much current without overloading the armature.

A generator/regulator test bench is easy to fabricate, and you don't need a variable-speed motor. Just use a 1/3 HP 1725 RPM motor, and run the generator at about a 1:1 ratio with the motor (Same size pulley on the motor as the generator). Put a 0-150 Ohm variable resistor in the field circuit that can handle about 5-10 amps and control the armature voltage by varying the resistance in the field circuit. That would be a good way to use that Niehoff Volt/Amp tester, as well as using it as a portable unit.
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!