I note in passing that the diameter limits for a 76AK-2 prop on a Continental are max 74, min 72 (many folks think it is a 76 inch diameter propeller).
Using a 1B90-71-42, on an O-200 powered J-3, I get about 2550 static, and about 2640 during climb. By comparison, a 1B90-74-41 statics at 2500 (about the same static as Roger's ?74?-40) and climbs out at about 2600, but the 74-41 isn't legal on the O-200 yet.
Based on my experience, I'd say if you have a C90 lying around use it. If you have an O-200, use it. If you have both, use the one that's most convenient.
