It only takes one pushrod through an old oem rocker at a really less than optimal time(where it kicks a lifter out and now you have 2 psi oil pressure to try and limp it home) and location for you to question when you would ever use them again in a "high performance" application.

The XE series of cams have much faster ramps than the oem cams the rockers designed for.
If you have access to a new set of the old MP HD stamped rockers that's a different situation than using a set of 30 year old stockers with an unknown history.

If I had some 273 rockers on hand, I know what I'd use(but then, I've already had the pleasure of putting a pushrod through a rocker with my old school .480 lift cam, at midnight, when I'm 20 miles from home and the oil pressure gauge is barely up off the "0" peg).