I need an alternator that will charge at SLOW SPEEDS

Hey guys:

I am still tweaking the '71 Valiant that you may have seen other questions on....

I'm not having any electrical problems per se, but just a small annoyance:

The junkyard-picked alternator I installed when I put this collection of parts together will not charge very much at idle.

With no load it's about 13.8v at idle, 14.5v at higher speeds.

With lights on and brake lights on, it's about 13.05V at idle and 13.8v at higher speeds.

It's also rather noisy even though it looks like a reman unit(that means a lot, I know), so you think this is just sick or is there another alt that would charge better at idle?

I don't much care about high amps since this is a stripper with no AC or stereo.

Thanks!