That C/R sounds Right to me . But I would still go with that XE262H camshaft . First you should have 10.1 C/R or more for them Thumper Camshafts . Also you will kill all your Low end Torque with that Thumber Camshaft . And with that Power-Glide Trans you will not want to do that . The 75cc Heads that you did Talk about will need to have the 1.94 in Valves installed . The Z/28 Springs will work Fine Good to 490" Lift . You will also need screw in studs installed . As For a Price on the #461 Fuelly Heads ? Rebuilt set $500.00 Need Rebuilt $200.00 .