Assuming that you have the original rear end with 4.11 gears, and assuming you are running a bigger optional tire like 6.50x16 (29" tall) you would be topping out at 63MPH which is 3000RPM. That is also assuming that your 235 is '55-'62 vintage. If the motor has been re-built and balanced this is your max. speed. I wouldn't run any 235 over 3000RPM max. If you have an early 235 from '41, it has babbitt bearings, in that case I would not push it over 50 MPH 2380 RPM.
