I have a 1963 Plymouth sport fury convertible with the original 318. I have a few worn valve lash adjusters on this engine. The adjuster screws have lost some of their interference fit. After adjusting them they turn themselves back to an excessive valve lash setting. I want to go through all the rocker adjusters to restore them to their original condition. These rocker screws do not use jam nuts to hold their adjustment. Are there any replacements with jam nuts for these rocker adjusters? I see Kanter sells replacement rockers for this engine. I have also seen on Ebay a rebuilt a rocker assembly. The rebuilt rocker assembly is said to be for hydraulic lifters only. The rockers assembly is shown clearly as from a 318A not 318LA. The 318A was designed only for mechanical lifters. How can it be possible to convert this engine to hydraulic lifters? The ebay add is for 1957-1966 318 rebuilt rocker assembly. Ebay number 1212 6448 2571. I am looking for some ideas for possible repair options.