I'm really trying to hit the 13 mark with my truck, the mod list includes..
5.3 n/a, longtubes, cai, 373s with truetrac, and wheatley tune, and the best i can get is 14.00, and a handful of 14.1s. These times are on a 295/50/16 et street. I'm hitting drive pretty close to the traps, and was wanting a lower gear to put the engine up higher in the rpm range for a better pull. The 295s are roughly 28" tall, so should i get 4.30s? 4.56s? Thanks

 

4.30s with a 28 inch tire seems to work pretty well. However if your on et streets a converter would help a little more, say a 3200-3400 9.5 converter would gain you .5 to .6 on you et vs .2 with a gear change, and you got much less rpm drop in the shifts so hitting third a little before the trap wont hurt you anymore.

 

Have you thought about doing some weight reduction to hit that 13.99?