O.K. Myth buster time. There were no early hemis with 1/2" diameter valve stems. The truck and some IND engines used sodium filled exhaust stems which are 7/16 diameter. There are NO known truck engines which used solid lifters and adjustable rockers. NONE. EVER. Only the marine engine and 300 series used adjustables. For a mild street rod, the heads can be made to work. Aftermarket aluminum timing covers are available. I have the trans adapters in stock. Feel free to email me with your questions.