Don't know... I was about to buy a set of them myself for my 3.5... They claim to have lots of racing experience, and they have a THICK bearing surface that is better for debris handling... but I don't really know if that is a good thing or not.
Well after posting this i called SRS in greenville. And called my best friend and so far I have heard they are pretty good. I think I might give them a try Have not started my rebuild yet since running into some snags. Once i locate a couple different heads I will start the rebuild after they are serviced.