Disappointing yes, but it's the first time out with the new combo, so no biggie. My main concern was how the converter would perform, but with the spinning issue, your not gonna get a accurate refection of what's going on there. You should be able to hook a 8" tire pretty well with the power level your at.
Two questions.........
1) I know you picked up the tires for a bargain. How deep are the wear holes on the tread? If there's little to no depth there, they might be past there lifespan.
2) Are you still sprung with the leaf's or has it been converted to coilovers? Just wondering how much adjustability you have.