Hey guys- I'll be putting the following cam in my Pontiac 455 COMP XE268H

I've ".0" Decked the block and I'm using a set of ported stock 6x-4 Pontiac heads with a set of Comp 1.65 Roller rocker arms.

I'm wondering about piston to valve clearance because of the 1.65 rockers and I zero decked the block. I'm pulling a much milder cam out so I was worried about the increased lift.

Also has anyone run this cam before in a pontiac? COmp said i sould have 17 inches of vacuum - Is that enough to run the brakes, tranny (TH400) and Mallory HYFire Ignition?

Comp XE268H

Gross Lift - .477-.480
Duration @.006
Tappett Lift 268 280

Valve timing OPEN CLOSE
@006 Intake 28 60
Exaust 74 26

Duration @ .050 224 - 230
Lobe Lift .318 - .320

Thanks alot for any advice or general help.