Customs 10SI or 12SI

I'm going to replace the generator/regulator setup in my Sky Hawk with an alternator. Which would be the better alternator, a 10SI, or a 12SI?...

 

It really depends on the car's electrical requirements. The production 10 SI maxed out around 60 amps, while the 12 S1 was around 90 amps. The cases are externally the same size; it's the cooling fan and air intakes at the rear that's different. The aftermarket 10/12 SIs vary somewhat in amperage output and fan case design.

 

Some 12si alternators were 78amps.

Stock 12si alternators have a plastic cooling fan. This may, or may not fit into your "theme".

Otherwise, it is down to amperage.