If your gonna be runnin' alcohol or racing fuel you could use those heads but a 64 cc head with flat top pistions runs over 12:1 compression. I have a 406 with flat tops and it's 10:1 compression which is borderline with 93 octane. but if your goin' preformance you will have to rework those heads to get them to breath right and that's alot of work so why not get a used 441 ? thier pretty easy to find....