Eddy heads what rocker arm assembly should I use?

Hey all I have an issue that I wondering if any one else has run into this. I installed a set of eddy 60779 heads on my stroker 408 small block this winter and when I went to start it up it sounded like a sewing machine. It is a 1975 block it came out of a van I'm running a comp cam XE268H. Edelbrock claims that you should be able to run with the stock stamped steel rocker arm assembly and push rods so, is this true or do I have to invest in a after market rocker arm assembly with ajustable push rods? The sound really didn't sound like a clapping noise from a loose rocker arm it sounded more just like a sewing machine running. The question that I'm asking is how do you check your preload on the lifters or how do know if you need a longer push rod or not or even if the push rod is to long? As you can tell i'm very lost and frustraited right now and don't know which direction to go. I didn't let the motor run very long for fear of hurting something. Have any of you done this combination before and resolved the problem?
Pat Faley
67 NB S Clone Barracuda
Peoria IL