19.5 tires/wheels on a Chev 3500

I heard the new GM's have larger wheel openings, but have not seen it myself. In the past, you could not cut the front wheels sharp and compress the suspension at the same time without rubbing. Some people trimmed back part of the liner while others cranked the torsion bars a little tighter to add height. I had 245's on my F250 and hauled 4000 lbs while towing 8000 lbs. My rear axle weight was between 7000-8000 lbs based on what I carried and towed.

Your AF992 will be heavier than than my AF811, so I would not attempt this without rims and tires rated for less than 4500 lbs each.

I'm close to you if you have more questions.