i have found an england game (and i'm sure there are others) containing three future city players.
28 sep 1946 at windsor park belfast
northern ireland 2-7 england
goals:
1-0 1min carter
2-0 7m mannion
3-0 28min manion
----
4-0 56min finney
5-0 61min mannion <== hat-trick
1-5 70min (lockhart)
6-1 80min lawton
7-1 83min langton
7-2 88min (lockhart)
england future tigers:
raich carter
wilf mannion (hat-trick)
neil franklin
england played three more games in 1946 and the same three played in all four games. they beat ireland 1-0, wales 3-0, and the netherlands 8-2. mannion scored three more goals and carter 2. (lawton scored 4 against the netherlands).
there were several more subsequent games with three future city players in them over the next couple of years. stan mortensen appears to have replaced carter for the 1947 10-0 win against portugal (lawton 5, mortensen 3 on debut, by the look of it). it looks as if carter and mortensen never played together for england.