I just finished doing the VSS on my 99 sohc. I bought the Felpro head gasket set b/c I needed the valve cover gaskets too and when I called a few dealers the price for the seals and gaskets was twice as much as buying the whole Felpro set.
It claims to contain "premium valve guide seals", whatever the f that means. When I finally finished the job the truck didn't smoke at all and doesn't appear to be leaking from the valve covers any more, either. I guess time will tell how long the VSS hold up. An availability search showed the Felpro set available at an O'Reiley's close to work....That gasket set was $167.00...