alternator question; how do you tell the difference between small vs large case alt?

I have no idea what alternator I have on my car. I cannot find any markings on it whatsoever. I need to order a larger output alt but don't know whether to order a small case or large case alt. I have a March Serp. conversion kit on there and whatever alt I have on there seems to fit and I don't want to risk ordering something different that ends up not fitting. I put a measuring tape around the back of the alternator and it has a circumference of 44 cms. Does anyone know the measurements of a small case vs. large case alternator in terms of circumference around the back of the alt?

regards,

jS

Tim65GT said:

Maybe this will help...

http://www.alternatorparts.com/ford_motorcraft_1g_type_large_case.htm

Click to expand...

Whatever alt I have only "just" fits. If it is a small case alt and I end up getting the wrong one, I am afraid that it might not fit. If I have the large case one, then I guess it would it be ok. But the key is knowng what I have in there now, which I do not know.

Tim65GT said:

OK, I just measured mine. It's a small case 3G from a 94 Mustang GT 5.0.

It came out to 48 cm circumference around the back of the case.

Click to expand...

Then I have a small case. Mine measures 44 cm in circumference around the back of the case and it is a pretty tight fit. Thanks so much for the clarification. Now I know which one to order.

after edit:

I just ordered a 150 amp alt from PA-Performance. Between the electric water pump, the electric fuel pump, the electric fan, and the electric vacuum booster for the power disk brakes (and the eventual stereo), I am sure that I will be right where I need to be.