Broken valve retainer parts and pistons with valve strikes go together. The engine has a “knock”, the pistons upside down. This is not a coincidence.
No, you don’t “need” those parts. But if you start pricing out what it will cost to have the old stuff reconditioned and machined you’ll find the new, much improved parts aren’t out of the ballpark. In some cases, like the rods, new is cheaper. Reconditioned rods with ARP bolts cost as much as new stuff, which is lighter too, reducing the rotating mass.