Do you have ARP bolts? I would assume that you do not. You may have over tightened the studs/rockers. Before they break, do you hear metal on metal noise? Have you checked your valves? and/or piston to valve clearance?
to get the proper length you need to take it to a performance shop that has the tool to measure it. It looks just like a push rod but is adjustable. basically the roller tip of the rocker should be center on the valve.
What kind of rockers? Stud or bolt down?
Were the springs replaced when you swapped cams? If so, which ones did you get?
Were the pushrods replaced when you swapped cams? If so, which ones did you get?
What procedure was done when the rockers were installed?
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