True that Smooth, Tenille love gilmer drive kits, as above you have to spend the cash on a quality unit. Mate of mine bought a cheaper one it's now in the bin. I have a straight cut belt on my supercharger and it screams. ( it's a bit too loud)
You need to be able to twist the belt back on itself 1/4 to 1/2 turn. I also had a Peter Jackson gear drive in my old police pursuit VL and it was superb noisy at low speeds and quiter at high rpm. I would expect you might already have a gear drive in your engine (500hp) plus you might need one.