We need a little more detail: Year, make and model of the vehicle.
The problem here is that there were 2 types of 6.00-16's: One for cars, and one for trucks.
In trucks, the problem is the narrow rim. A 6.00-16 requires a 4 1/2" rim - no range, just a single entry. It's 28.8" in diameter and 6.8" wide. It carries 1430# at 45 psi (LR C), 1690# @ 60 (LR D), or 1920# @ 75 (LR E). (only SRW entries listed)
The smallest 16" currently available is an LT215/85R16 and it requires a rim width a 5 1/2" to 7", has a diameter of 30.4" and a width of 9.3", with load capacities of 1940# @ 50 psi (LR C), and up to 3000# @ 95 psi for LR F. (only SRW entries listed)
For cars, A P205/70R16 requires a rim width range of 5" to 7" with a diameter of 27.3" and a width of 8.2" with a load capacity of 1565# at 35 psi. My books don't go back far enough to list the passenger car loads for the 6.00-16, so I'll have to use the archive at work.
You should be aware that Coker tire sells tires for vintage vehicles.
So while you're telling us about the vehicle, I'll go look up the stuff in the archive.