I figured I would post a follow-up now that I have some tires. The 11.5's fit on stock wheels almost exactly like the 255/50R16 Street Radials do. They don't leave much room for expansion but they fit great. I attached some fitment pictures. It's a dark cloudy day so it's kind of hard to get a good shot with my phone.
Looks like they are too big...
Side by side reference with the 255/50R16 (Right) and the 26x11.5x16 (Left).
Fitment is close but it works.
This is what happened to my old tires. Blew out at around 80mph, still no idea why.