I'm sure you can. on these old engines it's hard to tell what's what. i used the lighter 22r rockers on 79 20r stands and shafts only because the 22r stand screws were wimpy looking and stripped. other than that everything measured out the same. i don't know if you'll get any extra low end with a 20r head but having an extra 1000rpm's of power is a big advantage even in dirt. don't have to shift on a uphill to get it over the top and worry about missing a shift in some deep mud.
