1990 740GL higher capacity alternator available?

[5ft24]

Anyone know of a higher amperage alternator that will fit the 1990 740GL SOHC?
stock is supposedly 80 amp, but with new brushes/regulator and checking all the diodes, everything is ok, but turning on the headlights with a 12-14 amp draw, the engine RPM drops and even at higher RPM, the voltmeter is less than half way... at 3500 RPM, I get about 12.8 volts even with a new battery... if I turn off the lights, I get 13.8-14.2. made a new heavier ground wire, verified all connections were nice and clean and tight, checked battery cables etc, and it's just not performing as it should.
Also, My Girlfriends car needed a jump. Engine would crank slow, but the battery wasn't dead. Hooked up the jumper cables (Yes, connected them properly) and the Volvo Idle dropped, and after about 5 seconds the engine died. Started right back up, but really had to give it a lot of throttle to keep it running...
Thanks