If need be I can pull the valve covers and get the casting number, but for now they are newer centerbolt heads with self aligning rockers (I assume they are factory 1.5:1) I guess the only thing that would be suspect now would be the pushrods. I used to work for a Chevy dealer from '96 to 2000 and brought home many small blocks, heads, cranks & whatever I waranteed out. So most parts were early 90's & up. It's entirely possible that I used roller cam push rods with standard hydraulic but how do I find out?