What Stall do I need ?

Contact any/all of the converter builders that have been mentioned on this board in the past. Give them all the specs. on your setup, what you will be doing most of the time with the car and see what they recommend for you. This is the only way you'll get the correct converter for YOUR CAR. Just because a certain converter performs perfectly in my car, doesn't mean a damn thing unless your car and my car are identical.
Avoid companies that just resell converters. They may or may not have the correct knowledge on converters to fill your requirements. This is not a knock against them, just personal experience.
And don't let price be your main guide on your purchase. I've seen enough cheap converters apart to know you get exactly what you pay for.
JMHO