No, usually not "marked". If there's a part number on them, we can certainly "find" which they are.
Machined into the castings, below the rockers, where the pushrods come through the head, there's a "slot" machined from the factory (if early heads). If that slot hasn't been "drilled" to a 1/2" hole, the pushrod WILL bind in the guideplate. If these heads were original with "bolt down" rockers, something is "out of whack".
MouseFink, I've seen the roller-tipped versions of the "rail" rockers used with success on the shorter tips. They "clear" the retainer. If "stock" rockers, I agree.