Alternator problem ?

[Piratejason]

Okay, car is 1985 300D - turbo with over 280k on the clock.

For the last couple of weeks the fuel reserve indicator, batt. light, brake indicator and one other light have been lit while car is operating. Batt. voltage has maintained above 12volts and occasionally while accelerating gets up to 12.4volts.

I have replaced and adjusted to specs. the alternator belts.
I have replaced the voltage regulator with a Bosch from MercedesShop.

Is my alternator toast? I never see voltage above 12.4
Any tricks to try - dousing with contact cleaner, etc. ?
If replacement is needed any recommened ones that have correct pulley and don't cost more than $150 ?

Thanks,
Jason