He's got coil overs. He can preload the right side by cranking the adjustment ring on the shock body. Swapping tires before trying any of that may be a good idea also. If it still pulls right after swapping the tires, you'll know it isn't the tires.

Also, make sure you have equal pressure in both tires to start with. To get equal pressures, you need a very good tire gauge with the proper pressure range. A gauge that reads 0 - 60 psi won't measure very well down at the 5- 10 psi you're going to put in your slicks. They make crossover hoses that connect to both tires, so the pressures have to end up equal.