Hey everyone I am building a 351 cleveland right now I sent the motor to a machine shop here were I live told him what I wanted and my price engine cam back bored 30 over heads ported new cam springs all the good stuff crank all redone motor balanced . Now my question for you guys is I am running a comp thumper cam here is the part number cl32 601 5 he matched the springs valves everything but the rockers and push rods , he told me my stock rockers would work fine but it has me worried because my stock rockers only lift 419 from what I have read and the cam is 519/503 would someone please shine some light on this for me maybe I am missing something , also he told be that I wouldn't have to run headers that I could run stock exhaust manifolds on the motor now it's going in a 1954 ford f100 and there's not much room at all for headers thanks everyone's