What are you guys using for springs compatible with a 550-600 lift cam? Crowers springs are 1.050 O.D. and Comp is 1.509 (Dual). Comp also says head modifications are necessary...??? I know everyone is big on custom grinds but the guy doing my heads has run different cam profiles through his program and he said the 587 cam that Crower offers is right on the button for what I'm looking for (PLEASE CHIME IN IF YOU KNOW SOMETHING WE DON'T!). Have any of you guys had to make any head modifications? Also, I am staying with stock rockers so no need for valve cover spacers. THANKS IN ADVANCE!!!