camshaft help

Ahh.. well the car has 3.91 gears and runs a 27 inch tall tire. The car is a 4spd so no converter. Right now I shift the car at about 6K the motor is running out of breath above that, and it traps at 116.5 mph. With the new cam I hope to be able to stretch that to about 6500 - 6600 rpm. The car could use some steeper gears as 6600rpm in 4th gear would be about 135 mph but the car is mostly a street car so I like the additional cruising ability provided by the gears.