The 120 amp kit was totally different. It used a much larger alternator and the alternator was low mounted. I stopped selling the 120 amp kit since it was a pain to build and some customers tried mounting it into cars that it wouldn't fit in (A body).

The 60 amp kit is fairly fool proof and 60 amps is enough output for almost everyone. 60 amp Denso alternators are OEM on a lot of vehicles. My wife's SUV has a 60 amp alternator on it and that rig is EFI, heated seats, electric defrost, stereo, AC, dual heaters, etc.