Measure your tractor?
I assume the trailer is 6 1/2 feet between the fenders which is isn't bad.
I'm seeing the stock Ventrac 4520 is listed at 49" wide. Add another foot for each extra tire, and you're up to around 6' wide.
Ultimately, I think it will fit, but will be mighty close.
If you are loading with the mower attached, pay attention to weight distribution and the balance point. If the rear wheels are very far back, and you're towing with a light pickup, you may need to load backwards.