1973 340, want more power.

Rear wheel dyno results were 266.37 hp at 5900 rpm but was at 250 hp from 4600 to5400 rpm. And only 205 hp at 4000 rpm.
Max torque was 276.36 from 4200 rpm to 4700 rpm then started dropping off after that. At 3500 rpm it was only 245. My tires are BFG radial TA's. Not even soft street tires. The line for HP on the chart is like a squiggly line from 5200 to 5800 rpm. One reason I thought the cam might be the issue off the line is because Lunati states it needs at least a 4.10 gear and a 3500 rpm stall. My 3.91 with the 28 in. tall tires is no where close to what the say it needs, and my stall is a little under a 1000rpm less.
Even with the manifolds I thought it should be good for low 13's at around 103mph or so.