I ordered a full set of wheels/tires through whole goods. Great price.
As for your question, you should be able to put R1,R4, or turfs on it. Whatever floats your boat. You should know that an R1-Ag won't have quite the sidewall strength of an R4-Industrial for heavy loader work, but that's a issue you might get a fellow with R1s and a FEL to give you guidance on. I suspect there are a great number of guys here with R1s with FELs who wouldn't change to anything else. R1 guys tend to be that way.
So, to re-cap, fit isn't the issue, rather squatting or not under FEL/BH work. If you had turfs, R1s wouldn't squat any more, in my experience. I have had all three.