Max tire size - 68 dart

I wish I could fit 275 all the way around like on a duster

You can, you just need a 1/2" spring offset.

Yeah, I want more grip than these 255's can handle. Lol.

If you're still running michelin super sports that's a 300 treadwear tire, you could keep the 255 size and go down to a 200 treadwear tire like a set of falken azenis rt615's or bridgestone potenza re-71r's. That would add some grip.