Slipping clutch

I have a 1991 K1500 4x4 with the 5.0 and 5spd(169076 mi. Current). I replaced the flywheel, cluth disc and pressure plate about 6 months ago (163000 mi.)Due to slippage. After installation, truck shifted like new again. Recently, the clutch has started slipping again but only under heavy acceleration or high engine speeds. I'm not sure if having 35in. Tires with only a 3.42:1 gear would have any thing to do with it. If gearing and tire size are an issue, would changing gear ratio improve my situation? I'd rather not being as how a ring and pinion set for the front is twice the price of the one for the rear.