Dont quote me, but IIRC, performance rockers for the GM 3800 OHV work. Its been awhile since Ive looked up anything for that engine. Usually they are sold in sets for six cylinders, though.
Additionally, although I couldnt do a side-by-side comparison, the roller fulcrum rockers out of the '01 3400 look exactly the same as the part on the '98 2200.