I'm helping out a friend who's in a jam with his 2003 SC430. He has a bad alternator that needs replacing.

There are two alternators for these cars but there is no distinction as to why (option packages?):

2002-2010 use a 130 amp

2003-2010 use a 150 amp

Other than the VIN, is there any way to tell by the options on the car which you are supposed to have? Will it harm the car's electrical system in any way to use a 150 amp alternator on a car that came with a 130 amp unit?

 

They all came with the same options. It will not hurt in anyway to have 20 extra amps. Im looking for a 180+ amp since I have a large system

 

I could be wrong, but I believe only early 02 sc430s (made in 2001/01-2001/05) have the 100 amp alternators.
The later SC430s have the 130 amp alternators.

 

+1, agreed - it should be no harm in going up to the larger capacity alternator...