340 performance?

And what tranny?
Here are some estimates for 104mph, and 27"tires
with 3.21s
With an auto he could be trapping in Direct at 4100ish, or 2nd at over 6000.
With a 4spd he could be trapping in 4th also at 4100, or 3rd at 5800.
3.55s would increase these Rs by 10.6%; so 4500/6600 for A/T and 4500/6400, for M/T,
4.10s would increase these Rs by27.7%; so 5235/7700 for A/T, and 5235/7400 for M/T

13.8 sounds pretty good for just a lumpy cam and skinny street tires