The plastic rocker arm buttons used with the 6.5 rocker arm assemblies came up recently here in our forum, which reminded me of a photo that member MJ McCarroll sent to me some years ago. I think it's worth having a look.
As I recall, MJ used a specially hardened tap to thread the holes that were formerly used by the plastic buttons, then added bolts and brass washers in place of the plastic parts. I'd recommend using Loc-Tite 272 on the threads of the bolts.
My experience with the factory plastic buttons has been a good one. I've not had a problem, though I do replace them whenever I do cylinder head work.
Through the years, I've heard from a couple of other 6.5 owners who had varying degrees of problems with plastic button breakage. In one case, the buttons kept breaking even after replacing them... I suspect the root cause was a problem with the valve train that was causing the breakage (i.e. bent rocker, bent pushrod, bent valve stem or something other).
I liked MJ's idea, so I thought I'd show you all what he did. Thanks MJ!