i have a 521 that is going together and when i went to put the pushrods in they are binding with the guide plates. they are hitting not so much on the sides but in the middle portion in the back of the guide plate. I am runnning comp cams guide plates with dove heads 3/8 pushrods hi tec comp cams. i was out of answer on this one so i had a set of comp cams 8.550 5/16 push rods ans manley guide plates so i switched them to see what they would do because they were on the old 429 that i built with the same heads and they fit fine. well i was thinking with this new motor that i should go 3/8 because i am running a roller cam with .680 lift and about 625# open pressure i thought all i would have to do is change the guide plates and pushrods and it would be fine. I am also running scorpian 1.73 roller rockers . any thoughts would be greatly appreciated