Nitto makes an NT-05 that is sticky/tacky and they have a 245/40/18 so you'd get a little more tread to the road. Don't know what the price is though A 275/35/18 will probably rub; you could try rolling your fenders and using a hammer on the inside of the fender well if it just needs a little "adjustment". Not sure how a 275 would fit on your 8" rims though but I'm sure it's been done before. Good luck!
1-7/8" ARH LTs, 3" Magnaflow exh.,Spec twin disc clutch, 402 stroker , Fast 102 w/Nick Williams TB, 1000 hp shaft & axles, cam, fuel & suspension upgrades. 500 rwhp, 484 rwtq