BobE wrote:

This cam is very similar to the cam I’m running, although mine is a roller cam (Comp Cams), I have 1.6 rocker arms.  The listed RPM range for my cam is 1800-5800.  I suggest verifying with your cam manufacturer the RPM range for your cam.
 
Some data for you to consider.
With a 3.0 rear and a 0.68 5th gear, the rear end ratio would effectively be 2.04. 
Using 2.04 as the rear gear:
In 5th gear, at 60MPH, the RPM would be about 1600.
In 5th gear, at 70MPH, the RPM would be about 1900
In 5th gear, at 80MPH, the RPM would be about 2100
 
With a 3.25 rear and a 0.68 5th gear, the rear end ratio would effectively be 2.21. 
Using 2.21 as the rear gear:
In 5th gear, at 60MPH, the RPM would be about 1700.
In 5th gear, at 70MPH, the RPM would be about 2000
In 5th gear, at 80MPH, the RPM would be about 2300
 
With a 3.55 rear and a 0.68 5th gear, the rear end ratio would effectively be 2.41. 
Using 2.41 as the rear gear:
In 5th gear, at 60MPH, the RPM would be about 1900.
In 5th gear, at 70MPH, the RPM would be about 2200
In 5th gear, at 80MPH, the RPM would be about 2500
 
 
My 65 w/tire size similar to yours, 3.89 rear, in 5th gear my rear end ratio would drop to 2.45.
In 5th gear, at 60MPH, the RPM would be about 1900.
In 5th gear, at 70MPH, the RPM would be about 2250
In 5th gear, at 80MPH, the RPM would be about 2600
While I’m comfortable with this setup, I’m may go to 3.70 rear that would reduce the above RPM numbers by about 200-250.
 
Hope this helps.

Thanks good info looks like a 3.55.1 or the 3.89.1 would be best for me