So my current tires are showing some dry rot and cracking so looking at a complete swap of all 5. Bouncing between sticking stock or going to 37". Majority of time will be on road, trailering a SXS, and some occasional off-roading (Eastern Pa rock) but nothing crazy.

Anyone have the Continental TerrainContact ATs in stock size. Honestly wasn't even on my radar and not sold on it due to passive tread look but I have had great experience with Contis on other vehicles.

Oh also I dont have the rear tire carrier so my spare is inside with the stock bracket. If I moved to 37 on the spare would the stock holder work as this might break my spirit moving up in size.

 

No idea on that brand but one thing to keep in mind when going to a larger size that the vast majority neglect to bother with.... Also no idea of the inside spare would still fit if that were also replaced. That being said, you can run an off size spare for a short distance at lower speeds without issue. Just do not want to run that way for long though as it puts quite a lot of extra stress on the differential. Only for long enough to get you somewhere to repair/replace the tire. In any case, I'd strongly recommend that a spare being within about 3/4 of an inch of the height of the other tires. Narrower is fine and even different tread is fine though (although still not ideal for long term driving). https://tiresize.com/ has some great tools for comparing sizes, seeing how far off speedometer, etc will be.

Your speedometer, odometer, shift points will all be off, lower fuel economy and off the line power, but slightly better economy in the interstate as it will be running at a slightly lower RPM.

These can be corrected with a tuner or a full custom tune. When adjusted for the different tire size, besides just correcting the speedometer and odometer, it also adjusts the transmission pressures and shift points.