if stock heads you are not going to get much out of them for HP with out doing alot of work you need to tell us what you want for HP and go from there you can tie up alot of money in heads if they need alot of work it is a time /money thing i can tell you what that i would charge to go thru a set but that will not help out you need to take them to a machine shop and see if the cores are any good to start with ok i see 300HP