I've been running the Toyo 37's on stock fenders for about two weeks now without issue. I've not had the chance to jump it, but it has been stuffed and nothing seems to rub. I managed to keep the liners in and keep them sort of okay looking. You pretty much have to stick your head into the wheel well to really see the modifications.
I didn't take pics of the whole process, but these pics should show the general idea. I started by hammering the pinch welded seems on the cab. The next step was pulling out the liners and removing the flares. I did all of the trimming with a small hand saw and a pneumatic cut off wheel.
Stock, w/o flare. Not my truck...
Fender trimmed up, liners slotted and zip tied to lip of fender.
Flare trimmed, it's lip is about 1/2" wide now and allows the tire to tuck inside.
From the outside, it's not readily apparent how much cutting has been done. This modification yields 3.5" of extra clearance for the tire. I'm using the 37/12.5 Toyo RT on 0 offset Methods. If I had the 37/13.5 Toyo MT, I think the flare would need to be trimmed to less than a 1/4" lip to have any chance of that tire clearing.
I like the look and proportions of the stock fenders, and I don't have to deal with fitment/quality/cost of fiberglass. I think this is a viable option for running 37's, as long as you don't mind cutting. My truck is a 2010 with 93k on it and has been beat on extensively, so it's a perfect candidate for this mod.
