I have a GT6 engine in my TR6. The rocker shaft lost oil and shaft and rockers are destroyed. I'm replacing the shaft with the cheapest shaft I could find and in my pile of "somedays" (the stuff the wife calls junk) I have almost two sets of rocker arms. One type has a "spine" almost accross the top and the other type has a recess or "dish" where the oil comes out on top. Is there a real difference between the type or is it an early/late thing and is one better than the other. The originals in this engine are the "spined" type. Another question. Can I reface the area that pushes down on the valve or is it hardened. There is some wear and it makes adjusting dificult. I actually want to use the worse type since this engine is on it's last legs but I need it until I can pull the '76 TR6 engine from my '74.