So this is the guy behind the Rimmer Supercharger from about 10 years back? This 2.5L kit looks like the pic below. It uses a Clifford Performance intake.
The 4.0L kit is very different then before. The original kit also used a new manifold. Looks like this time he keeps the stock manifold and bolts on an adapter plate.
Old:
New:
Though getting back to the original question, I'd regear. it should cost a fraction of what a SC costs and you don't have to move up to Premium Gas. I'd go 4.56's if you're going to stick with 31's or maybe even go with 4.88's and lose some top end of more grunt down low. You'll probably want to calculate your RPM's for at least 5th gear and see where it runs out at.