I have alway used stock alternators until the one on the truck fails, then replaced with the largest one available, Last year I replaced one for an 85 K20 there were 2 avaialable I believe a 70 amp & an 98 amp, put the 98 amp in, this was from Pepboys I believe, I know there is a place in town where I could have had it rebuilt or the could have made it put out more amps. Never had a need, I run plow, highlighter bar & headlights. My new truck 99 order with plow prep only has a 110 amp, that has computer ect to run.