I am curious as to why you would like to know specifically what speed you are going at 2000 RPM.
There engines give more bang for the buck considerably above 2000 RPM. The sweet spot is between 2400 and 2600 RPM in my experience. Upwards of 3000 is not an issue either if you need to go highway speeds from time to time.
These engines tend to lug at 2000 RPM.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission