A 6-foot tiller sounds pretty big for a TO-35. It would probably depend on the type of soil where you'd be using it - sandy loam,it MIGHT work; hard clay or caliche I'd consider out of the question. You have around 33 PTO horsepower to work with. Look at specs on different tillers and see what they require and what their limits are.
Personally, I'd go with something smaller, probably 4', at the most 5'.