I had Dwayne Porter grind my solid flat tappet cam in my 63 and we went with the EDM lifters which I bought the cam and lifters from Dwayne. The lifters came and were in a Comp box as they are EDM lifters with the small oil hole on the bottom and they looked like 2 piece lifters to me as they had a snap ring in the top of them and an oil hole in the ceter like they will work for pushrod oiling if you want. I did not use them that way as I use a solid pushrod and have stock rocker shaft oiling with my standard EZ heads. All has been fine as my 493 has been together and running good for 2 years. My cam is actually close to the .590 as it has .592 and .585 lift with 264 and 270 @ .050. But mine have been fine and all looked good when I adjusted the valves last summer. Ron