Tough one, Probably Diazepam and oxycodone. Though if we factor in market price & availability of present day in my country, probably H and alprazolam.
Salvia and Sativa or Salvia and kratom, in this reality.
If it were an endless supply of anything, crack! I'd probably perish rather quickly. I would have to have left my heart behind, though, to go back to it.