For the ST G51s that I have built up with Gardner P&L sets, I searched out well used R/C versions for those, I assume you want the control line piston and liner. I don't thing the R/C liner can be retimed, but not really sure. I'll be digging in some of my stuff today and I'll double check, but in case you were not aware there is a difference in the R/C and C/L liners, and I think that is the only difference between them besides the carb.
  Type at you later,
   Dan McEntee