hi i am looking to upgrade my stock ex on my 496ho i have a 28 foot pantera with twins and the E top headers are wot iam looking at big outlay for me as i need 2 sets so any feed back from anyone who has used these header would be great ,allso they say i need 34 and half inch drive centers for them to fit do i mesure center of prop to center of prop for this mesurement ,my stock ex manifoulds only have about 3 inch gap max any help or addvice would be great thanks regards paul