Rocker studs snaping

To me, this look like you need to remove the rockers, loosen (replace in some cases) the studs so the guide plates slide side to side, reinstall the rockers to snug on the valve tip and move the plate to get the rockers to line up. Do not be surprised if you need to slot the plate holes that the studs go thought to get enough movement side to side to line it up. Stud height and push rod length may need to change to adjust rocker geometry so I would mock up what you have to see if they are the correct length.

This get fun on a canted valved heads like Fords 335 and 385 family and Twisted Wedge heads that have compound push rod angles. A lot of guys use a light weight valve spring to do the mick up.

The problem is who knows what Edelbrock used for rocker geometry to determine the stud length they send. If you took 4 to 5 Magnum based rockers from different manufactures non of them would be the same (unless they are rebranded).

Looking at how the studs broke it look like the rocker was twisting the stud until it broke.