Cat 3 refers to the 3point, which can be regular cat 3 - or it can be cat 3N, which is the same dimentions of a cat 2 with bigger holes that are easily bushed to work just fine with cat 2 stuff.
A real cat 3 3pt hitch can often be narrowed & bushed down to 2pt dimentions by shifting the linkage some - chain, bar, or rub bar.
The 1000 rpm thing is a different issue, that is a 540 vs 1000 rpm pto. Most tractors of your size allow the use of either speed, often with a replaceable stub shaft on the tractor.
It is possible a cat 2 phd would also have the option to go 540 or 1000 with a different gearset/ shaft option. I'm not really familiar with a cat 2 phd, must be heavy duty! /forums/images/graemlins/smile.gif
I would not want to use a 1000 rpm tractor with a 540 rpm phd, as you want the digger to go about as slow as possible to start with.
Would help to understand the exact issue some, you kind of mashed a couple different issues together?
--->Paul