The Direct Connection chrome valve covers may be a little taller than stock? If you look on the Harland Sharp website, I think they indicate their rockers work under stock valve covers with cams limited to around .500" lift. Mine work with stock 69 steel valve covers with a .510/292 cam and previously were fine with a .500/310 cam (that had a little longer duration and was higher reving). Both blocks were decked and heads had been milled .020".