just from my experience you will not change much by dropping to the lower gears. Your RPM's are close to where you need to be. My experience is from two drag cars. I had a 48 Anglia with a 340 4-speed, used to race 1/4 and 1/8 had 5:12 gears for the 1/8 and 4:56 for the 1/4 one time did not have time to put the 5:12's back in for the 1/8 and it ran exactly the same, I just did not shift into 4th. I recently had a 64 NSS car ran 9's It liked 4:30 gears 1/8 or 1/4 tracks tried several ratios. Just my experience others may vary.