Ok so I am ordering the finishing details for my 455 and I want to go with a new crome alternator, for my sexxy new engine. But as I was browsing Summit, I see that they have 100 and 140 amp alternators, which one do y'all think I should go for, the engine has A/C and I have a 500 Watt Amp for speakers.

 

Choose the alt with the highest output at low RPM. That may be the 100 amp alt. You will have to do a little research to find out which one that is. You haven't given enough info to give a good answer. What type of alt are these? 10 DN 10 SI 12 SI CS130? Often when an alt has been modified to achieve higher amp output, it will have an altered output curve, meaning the amps at different RPM have also changed. A typical stock CS130 alt capable of 100 amps at highrpm will put out about 40 amps at lowrpm. When the stator is changed to make it 140 amps, it will put out 140 at highrpm and 30 at lowrpm. A cs144 alt in a stock amp design would be the best choice. It can put out the 140 amps you are looking for.