Ralph, For what kind of automobile. Different sizes of alternators may or may not be any better than another. Just bigger and more costley to make or cast. Your question is a good one but more info is needed. Diodes and regulators and there quality is the problem. They are also made to be marginal in performance so we will have to buy more some in the future it keep people working. If you will read the specs on the original De Lorean alternator, you will understand why it doesn't work in the U.S.A. 80 amps, at 68% F, it will put out the current at 3000 rpm with nothing turned on, what were they thinking. Your never going to idle. Someone didn't think of export to other country's when this was designed. I can tell you that the 140 amp I sell for $195.00 cost the same to build as the Farrar and it sells for over $500.00. My $0.02c's worth John