The only 'problems' I see with their tire/ratio chart is that it obviously was intended for use for off-road trucks. The tire sizes you see listed on that chart would be much, much too big for our classic Cats. That and the gear ratios were too high for many of our Cougars. Many of our cars came with 2.75, 2.79 and 3.00 gear ratios. I'll have to see if I can make a table more suited to our Cougars...
I was running G-60-14 bias belted tires on AlphaCat. They were about as big as I'd want to go. Today they'd call that size P245/60/14. They were 25.5" diameter. The stock E-78-14s (P205/75/14) on our Cats were about 24.5-25" in diameter.
The formulas will work if you just plug in your variables.
Now, with all that said, if the inital post wanted to know about theoretical top speeds of our cars with the different gear ratios, I'd have to say that it would depend on what your limiting RPM would be, tire size and engine power. For most of our more pedestrian cars, you're talking about 5200rpm as a 'redline', a street/strip car is good for a bit higher like 6000 or 6200rpm. Tire size? say 26 as a ballpark. Power output? Let's just say that wind resistance gets real big at 100mph and can be the limiting factor sometimes for stock engines! You do the math. Plug those numbers in there and see what you get.