Turning 4.45s with stock cylinders on race gas is a pretty good run. As far as the 38 lectrons, thats a lot of carb for that motor. Not saying it can't be done, but you may have trouble getting it tuned in correctly. I'm running 39s on a 68mm bore 10mil stroke on alcohol. Gearing depends on an few things. Your launch rpm, track conditions, weight and engine setup. Go up a couple on the back and see how it reacts. If thats not it, go back to the 41 and drop down one in front.
All of this is speculation and its hard to tell without hearing the motor and watching the performance.