I picked up a '92 Z28 L98 long block without valve covers to put into an '89 IROC-Z L98 car that somebody swapped in a '86 305 LB9. Besides the silver paint, is there anything special about the '89 TPI valve covers or can I just go to the junkyard and get any center bolt covers off of a late 80's/early 90's SBC engine?

All valve covers should be the same from 87 on up. As long as you have the factory rockers.

some have differant locations for the pcv and breather but all the tbi and corvette covers will fit
90-92 tpi fbodys have the differant pcv and breather locations