Found this info guess I can go with 37x13.50r20's as long as it is spaced right....May need fender flares huh?

Will they fit?
Just about any 35x12.50x17 or 37x12.50x17 will fit on the H2 stock rims okay, although a wider rim may be recommended for some tires. It should also be expected that a larger tire may well rub on the front sway bar or frame of the vehicle at full lock. Although the stock BFG AT tires may rub slightly on the front sway bar, many of the 35" or 37" tires will almost definitely rub to some degree.
Due to the backspacing of the stock rim, anything wider than a 12.50" tire may rub heavily. If you wish to go with a 13.50" wide tire, a rim with 4.25-4.50" backspacing is recommended

 

There is another active discussion about this... and you pretty much already have what was being said there...

https://www.hummerforums.com/m_92055/tm.htm

 

yep