Good grief; I just looked up the specs.
I had NO IDEA it was only 3700 lbs as an open tractor.
{and I though K_word tractors were "lightweight" (-: }
I would guess another 1400/1500 lbs for a loader with bucket and maybe 1200 if you had loaded R4s on it - just guesses.
So I'm guessing you have the cab with unloaded R1 tires and no loader.
Anyway, for what you say you will be doing you could probably pull an 8ft box blade without any problem, though you would cover your tracks with a 6ft.
If you want to allow "rolling contours" side to side in landscaping work the narrower one would work better for that.
BTW, I'm in the North East (USA) and we call it "ROCKS", not "soil" (-: