im gonna start off by saying im into mud racing . im running a 408 bbc (396 .060 over) and just traded a set of tires for a pair of procomp heads part number pc3021-396. is has comp springs and comp roller tip rockers on them. the local machine shop took a look and said they r fine. I was wondering if they r actually any good.. what is their down fal regardless of where they r made. also ive heard that with a little machine work they can be pretty good heads .