valvetrain ?'s

hey guys im doing alittle work on my 302 right now and trying to figure out what i wanna run, its a street car that will get drivin hard at the strip, i wanna do comp cams products because there right here by my work and i got the hook up there through some friends that are employees. that being said, ive been looking at there new hi rev hydro roller lifters and there ultra pro magnum rocker arms, right now ive got a e303 cam in it, but im not gonna change it untill i put my 351w in it. also im sure im gonna have to change pushrods for a different length right? i was gonna get the comp adjustable pushrod tool to check for correct length. thanks guys.

Also ive seen where there are 7\16 stud sizes and 3\8 stud sizes, whats the factory size and will i have to remove my factory rocker studs for the new roller rockers, or can they use the oem studs?

its got a set of brodix aluminum heads on it, but they re-used the oem rockers (i bought it this way)

thats basically what i was asking what the size of the threads in the heads were, so i know what studs to get. im really trying to get some good insight on these motors so i know the right parts to get for the driving style i have, im used to biulding alot of import stuff, but im mechanically inclined i can do anything almost i just have to learn it if that makes any sense