In 1968 thru 1970,
It was either 'mill' your #906 Heads {.032"}, or pop on a set of stock 67' 440 'HiPo'
Heads on your {1968 thru 1970} 440 to get the same Compression.
Though some also claim that the #906 {1968 thru 1970} Heads had a slightly better Intake Flow at Higher RPM's.
Actual Results coming up,,,,,,,,,,,,,,
