Rocker stud to valve
Chevy small block 1.363"
Ford small block 1.455"
AMC V8 "same as ford small block"
Theoretically you can use a Chevy roller rocker set however you must start with the roller tip in the middle of the valve when the valve is closed (if your building you can start slightly past (+0.03, -0.00)
This means if you are using a bridged type head with a 5/16" hole you must tap the hole first and set the rocker in and take material off the boss accordingly to enable correct geometry. (You do not want the roller tip in contact with the retainer, you will drop a valve. Ford small block and AMC share the same rocker length and measurements however some mfg's like to make a thick bottom on the rocker and the AMC stud may require clearancing on the bottom of the rocker if they are the thicker type. Here are Harland sharp rockers, notice the relief They are the exact same rocker but the relief is cut into them for the AMC stud. It is possible to run these but a new stud must be used to get the correct valve goeometry.