360 974 heads which roller rockers fit?

This is similar to what you would need, except using standard rockers, not offset like W-2's have. But another problem is the fact that they make different heights and offset shafts & blocks, depending on the valve stem height. It was usually used for the much taller W-2 race valves. Harland sharp has been doing this for a long time. But you'll have to figure out what combination of parts you will need to get the geometry and contact patch you need.

Gotta watch the rocker-to- retainer clearance as well, especially if the shafts don't get offset away from the valves.