Looking at 3.91s and 30" tires... your trap rpm cant be very high. I'm guessing if the convertors any good that your not even touching 5500. I dont think any single plane, combined with that cam, will get you faster. Were the heads flow tested? I would suggest adding plenum volume first with a spacer on top of the sucker. I really think until you're trapping in the 6K range going single plane will not help you. It will move the rpm of the peaks up, and that cam doesnt support that idea well. I like to ignore the firs two gears, and set things up for high gear. Because you can always adjust shift points for 1 and 2... There's nothing you can do 'cept ride out 3.
