Ok now i see the problem. Unfortunatly to do it right your in for some dissapointment.
When you start upgrading the valvetrain you need to do more than just one piece at a time.
First im wondering how your locating the rockers?
You need some sort of locating device to keep the roller tip centered on the valve tip. Usually guide plates. Then you need hardend pushrods to go with them.
Another thing thats bothering me about this is you said that the "5/16 nuts" To my knowledge not even Pro Comp makes a 5/16 stud Rocker. If your actually using a 3/8 rocker on a 5/16 stud you are in for big problems.
To the nuts.
You cant run the stock nuts on Roller rockers. From the picture on pro comps website they appear to give you the poly locks with them. Use them.
The stock studs can tend to pull out over time and with non-stock use. Higher valvespring pressures, higher Rpms and just the additonall stress from peformance use can take the toll on press in studs.
Here is a mild performance setup for fairly cheap from Crane Cams.
Crane Cams 36655-16 - Crane Rocker Arm Guideplate Conversion Kits - summitracing.com
The only thing i cant figure out is how the studs install in the heads. Mabey they just form a thread as you install them. (Much like a roll form tap.) Dont know. If so then you have to be VERY carefull on getting them straight.
GL. Let us know.
I remember where i left my brain, this will only work with the pedestal style heads. Duhh.