becarefull with RPMs calculators... they don't consider the slippage AND the inertia of the car while riding, so just can take the rpms with engine pulling completelly the car.

there is a nice XLS table on the tech archives too.

and sometime ago somebody made an animated RPM calculator based on a 68/70 B body Rallye cluster where you could add a slippage % for the torque converter, as an estimate. Dunno if is still working.

as mentioned, with wheels on the air ( being SG, need to get both on the air ), a full turn of the axle/wheel will rotate the drive shaft the gear ratio. If single leg ( no SG ) you can raise just oen wheel andwill rotate half of the gear ratio