I went through this exercise when I found that my alternator could not deliver voltage reliably at low speeds especially when my electric fans kicked in. The solution was to purchase an alternator for a 1988 Chevrolet Caprice with the Olds 307. You will have to reclock it to move the terminals to the correct place so you do not get interference, but this is an easy task accomplished by loosening the through-bolts and turning the housing to match.
This upgrade ensures that you have maximum charging voltage no matter what your engine speed is and it significantly increases the reliability by eliminating the external regulator. I highly recommend this upgrade and it is indistinguishable from the original alternator from what I recall.

http://www.oreillyauto.com/site/c/detail/USL0/3351103/01468.oap?year=1988&make=Chevrolet&model=Caprice&vi=1037089&ck=Search_01468_1037089_2538&pt=01468&ppt=C0330
You will need a conversion kit to wire it up but it is simple to implement. Here is one option:
http://www.madelectrical.com/catalog/cs-130.shtml