Looking to upgrade wheels and tires but can't do both. Was thinking of going to 35's but didn't know the max tire width on the moabs. 35 12.50 too big?

 

no 12.50 is not too big

 

Spacers may help with rubbing unless they are illegal where you live.
35s will fit under stock wranglers without lift but if you do a bit of flexin they will rub.
12.5 wide tyres should fit but will bulg out like doughnuts and may be illegal where you live. Just ask your local arb or 4x4 tyre store about brands and treads as they are all different and they'll know best in most cases

 

Also beadlockers that go inside the tyre and don't bolt onto the outside may help with keeping the rubber on too