First off, unless you put it in there, your tractor does NOT have the DT-361. The 806 was ALWAYS normally aspirated (no turbo) and had the D-361 engine. It lacks one main bearing, has a smaller intercooler, and lacks piston cooling jets needed for turbo operation. That being said, there is NO WAY your tractor had a turbo leaving the factory unless it was a 1206.
The custom tractors were a cheaper version of the tractor that were usually exported, but some stayed in the US. They had fewer hydraulic valves, less fuel capacity, and fewer headlights. Obviously, they did not get a turbo, as they were meant to be stripped down tractors at a bargain price.
How much power is it making? Hard to say. Stock 806's have ~85 horsepower. Ours with a cranked up pump and normally aspirated makes 105 horsepower. Yours with the turbo it is probably making in the range of 110 to 150. Be very careful with this power! The 1206 had a beefed up rear end. With this much horsepower in that 806 chassis, one max pull could thrash the rear end. That rear end was built strong and had a very good allowance for overload, but I think that you are probably at or close to its limit. I personally wouldn't exceed 110 hp myself, but I know a few that are well over that and don't have problems. The motor probably won't have a problem with it if it is properly maintained.