A500/A518 Aftermarket Overdrive Ratios

3.91 X .69 = 2.6979 (2.70 rounded up.)
4.56 X .69 = 3.1464 (3.15 rounded up.)

1st get up and go numbers are;

3.91 X 2.67 = 10.4397 - 10.44 = very good
4.56 X 2.67 = 12.1752 - 12.17 = a bit much.

What size rear tire diameter? This can have a positive effect if it’s large.
Also, is this a hot street or 1/4 mile build? The 4.56’s point that way. If so….. Then the OD would just be gravy after the first 3 gears. A 3.15 final drive ratio and a tall tire would be really good.