There are early 413's & 383's with the 1.75 exh valve 4 bolt covers and stands for the rockers.Letter cars w/ram intake,383 8 barrel(915's?) and 413 2 four barrel engines.Harder to find but out there.Also the 63 300J had 915's with the old shaft assembly and 4 bolt covers.They didn't appear again until 67 with cast in stands and 6 bolt covers.You will need hard exh seats added.Unless you can do the work yourself it is probably cheaper to buy the aluminum heads out there.To me 516 heads aren't worth the effort (port match bowl port,valve guide work,hard seats and parts), flow poorly and are very prone to cracking with a large exh valve. A set of stealths or eddies look pretty good and really flow a great deal more air.
