how many batteries do you have and have you done the big 3 yet. that will help out too. email the guys at dc power inc. they don't list the grand prix on their website but you should be able to email them and they should be able to get you something. i've seen them build alts with 270 amps max output. i plan on using them when i get my alt. by the way what set up do you have in there. DC Power Engineering - Welcome that's their website. hope this helps out