I am using these ported Victor heads in a race only application.Mike at B3 Racing is currently building me a rocker geometry correction kit for the Hughes rockers. Since this engine is only 493cu. in.,I would like to be able to rev this motor to 7500 if needed. It is a solid roller,with 280*/283*@ .050 w/.690 lift. It appears that I am probably looking at a 1.90" installed height.Does anyone have a solid spring/retainer combo that they wish to share? The PAC reps seemed to be involved at a seminar right now. These heads are a challenge,but they should make some power if they really flow like they claim and I am able to get the valve gear right. Thanks, Bill