My first sammy had 35 BFG MT tires with a 4.3 V6 and open stock axles. I did a Spring over swap and used a set of used 3 inch lift springs. It could have cleared 37s with no rubbing. I sold it before I used it off road in that combo, bu the lady I sold it to used it for mud drags with no axle issues.
My current sammy has a spring over with stock springs and a single extra sammy leaf in each pack. It clears 33s no problem, and would probably clear 35s with some trimming. It runs 5.13 gears and I can take it up to 70 mph no problem. The rear is welded and the front is open. I've snapped one rear and one front shaft with this combo and heavy wheeling. It only flexes about 7 inches in the front or rear and rides stiff. I'm currently selling it on ebay, but if I were to keep it I would remove the extra leaf I put in each pack.