Use of lead substitute ?

No lead substitutes for me. I do use the best synthetic oil I can get though and oil additives like Z-Max and Lucas. As for the valve lubrication, the gas sold in the USA has alternate lubricant formulations that are sufficient. I had the heads to my 440 engine rebuilt and I asked the machine shop if they recommended installing hardened seats. He said "No - they're not necessary". He said that though the "lead" heads might experience some recession, it was not worth the high expense to install hardened seats in anticipation of the slow if ever at all expected problem. Save the money and do more frequent oil & filter changes.