Use the Xs.Unless you are road racing,run em.Been here,done that.Eddys,peak at
[email protected] head porting shop I worked at,built a similar 340,healthy X's,11.7 comp,solid roller.Ran 11.70s with the Xs,118 traps.Customer wanted Eddys,worked them hard.All he picked up was a tenth.My .02.