I am putting a 302 in my 1953 F100 and someone told me a 3.73 would work, but I am running 205/50/15 tires now. Is it gonna make a different with the tires when I put the 3.73 in?

 

If you have the original rear, It should be approx 3.90 to 1, so 3.73 is not going to be a dramatic difference.

 

Here is the formula I used.
MPH X Gear Ratio X 336 = RPM/Tire Diameter

Example:
70 MPH x 3.50 gear ratio x 336 = 87729/Tire Diameter
With a 27" tire diameter, this works out to 3048 RPM

You can adjust tire diameter and gear ratio to get the
RPM you want to cruise at. If you end up with an overdrive transmission, factor .67 or final drive ratio into the
formula: MPH x Gear Ratio X Final Drive Ratio X 336 = RPM/Tire Dia.