I have a 92 f150 with a 351w and it has 224,645 miles and I just blew a head gasket. Rather than just replace it I want more power and figure this is the best time to up grade. I've been looking around around at different kits and was wondering which is better the 408 kit or 427? Also if I do this and put on the gt40 heads what all do I need to change with the computer? Any feed back would be greatly appreciated.