I'm thinking that's the earlier carb. Maybe check out the Scepter Flite web site and see what they have. There was a guy in a local R/C that really understood Fox carbs and some how used a monometer to set the needle for proper to get them in the ball park, and then would adjust them for final run for people. At that time period, the .40 was considered the most powerful .40 on the market, if you could understand the carb and how to adjust it. If there was a major weather shift, you needed to know what to adjust for the temp changes and such. I never had to run one myself, and I think I may have a few carbs around here myself as I had a couple reworked by Lew Woolard for stunt. As I understand it, it's like any other carb. High speed needle is just for wide open throttle, and the low speed needle was just to get the transfer from idle to about 3/4 throttle. Is there an air adjustment screw on it? When OS came out with there easy to adjust carbs, that is what hurt Fox .40 sales.
Type at you later,
Dan McEntee