Surely it totally depends on the era. Back in Meads' day, lineouts, and rucks (in particular) were vastly different affairs than they are now. I would argue that a player as good as John Eales, as magnificent as he was in his time, would have struggled a lot in Meads' day, simply because he was not a mongrel.
I would agree that Eales and Giffin were a pretty good combo, as were Eales and McCall. Botha and Matfield would take some beating in any era, however. I would love to have seen Matfield under the old lineout laws, no lifting. I reckon he would have been absolutely unbeatable. And Botha would have been in his element in those days.