Internal Reg.alternator on 69 valiant?

The same voltage regulator runs all the different amp alternators. So the field current is no different, The internal windings of the alternator are.

The cars With few electrical accessories get the lower amp alternators the AC and power everything cars get the big amp unit’s.
No. Only amongst each line were the regulators the same. The optional 'fleet' alternators had regulators that were sometimes different. The '60 amp' Chrysler built squarebacks show a different regulator than the '50 amp' which was the highest normal option. The revised squarebacks came out later.