What gears are you currently running? I'm not a huge fan of big gears unless you're engine is built to turn a bunch of rpm's.
When I had the 340 in my Dart it ran mid 7.20's in the 1/8 and 11.60 in the 1/4, shifting at 6400 on 275 radials, 1.57 60' . It started out with 3.91's and I decided I needed more gear so I put 4.30's in it. The car picked up .04 in 60 and carried it through the 1/8. Not worth the money or time spent IMO.
It's currently running 4.10's with a 275, at 55mph it's turning 2900. Very easy for me to live with.
