Top Speeds from the installation of a big block engine is subject to many variables, its impossible to give a an exact number; such as:
1. Gear Ratio
2. Belt Tension
3. Clutch Condition
4. Tire Pressure
5. Road Conditions
7. Brake Drag
8. Carburetor Tune
9. Engine Rev Limit (Most small engines will have a rev limiter between 3600-4000rpm)
In general, the higher the engine rpm, the higher the top speed.
The chart below shows a theoretical top speed in ideal conditions based on tire size and cart model. The chart assumes factory gearing, intact rev limiter, and overall good conditions.
If you would like to increase your top speed, you can swap out your transaxle gears for 6:1 and 8:1 versions that will give you a massive increase in speed at the expense of torque. This is very common on the 1997+ Club Car and unlifted carts in general where low-end torque isn't needed as much.