That depends on your price range. You could use Xeldyne springs and valves, (they are used in a lot of the new & vintage racing engines. Think Indy car, nascar, drag racing, etc.) or you could use cheep PRC (China) parts. Or any where in between. For my 340/416 that I collecting parts for, Xeldyne is being used as I’m going to throw all the trick parts into that mill...
