"We've got a fairly good idea of what England are doing," said South African coach Dawie Theron.
"Our biggest thing was to get these guys 100 per cent ready because we haven't made as many changes as we thought we would over the last three games."
The Junior Boks pack has big bruisers such as lineout ace JD Schickerling and No 8 Aidon Davis, both of whom perform their core duties perfectly.
England, like South Africa, have been mostly impressive in this JWC, other than in the final pool game, where they were flat and almost dropped it to Argentina.
But they look to have real breadth to their game, perhaps even more so than their senior team.
They have the tournament's outstanding midfield pairing in Harry Sloan and Nick Tompkins, a dangerous backline weapon in wing Nathan Earle, and a clinical and multi-skilled pack. Halves Billy Burns and Henry Taylor control play nicely for them. Coach Nick Walshe has made only one change on the bench.
They know how South Africa will play it, and it will be a matter of combating that often enough.
"They are a good South African team, but they will probably bring what they have brought to each game, massive physicality and seeking to dominate their opposition," said England skipper Maro Itoje.
Both sides are also expert at driving from lineouts, scoring key tries in their semifinals. How they (legally) challenge those mauls could be instructive.
No 10 Handre Pollard, around whom South Africa base so much of their play, could become only the fifth player, and the first non-Kiwi, to win two JWC winners' medals.
He is also the only man to land a dropped goal in a JWC final (in 2012).
England, via wing Howard Packman, kicked one which took all by surprise in their semifinal shellacking of Ireland.
This decider could be so tight that a drop goal, a marginalised scoring method in New Zealand rugby, might be the difference.
Most of the New Zealand side would like to think South Africa can win it - a natural reaction when you have twice lost to an opponent.
Road to the final
South Africa
Beat Scotland 61-5
Beat New Zealand 33-24
Beat Samoa 21-8
Beat New Zealand (SF) 32-25
England
Beat Italy 63-3
Beat Australia 38-24
Beat Argentina 17-16
Beat Ireland (SF) 42-15
Today's JWC card
Eden Park
5-6: Australia v France, 2.35pm
3-4: New Zealand v Ireland, 5.05pm
1-2: South Africa v England, 7.35pm
QBE Stadium
11-12: Italy v Fiji, 12.35pm
9-10: Scotland v Argentina, 3.05pm
7-8: Wales v Samoa, 5.35pm