Well I run a 9.6 deck block.. and the 420 intake is for a low deck so I've had to use spacers to make it work.. I cut it in half and shipped it to Brett Miller.. he's going to stretch it I think close to 5/8 of an inch.. it will make the plenum larger in the runner shorter... the idea behind the collector is it has a 3-inch pinch. Versus the 2.5 that I'm running right now.. trying to find a happy medium between acceleration and mph