Yes, the code applies to ALL Boeing aircraft in the fleet that have been ordered by THAT airline. So, QF has:
B747-438, -338, -238B, SP-38
3 B747-400's have GE engines, 2 were MH and hence are B747-4H6's and the other was Asiana (I think - somebody can joggle my memory and tell if I'm wrong), and hence there is also 1 B747-48E. These 3 B747-400's were ordered by the other airlines and when they cancelled, QF picked them up but they retain the designation that were given them when they started being constructed.
B737-476, -376 - the -76 refers to Australian Airlines, which merged with Qantas in the early 90's with Australian de-regulation.
QF also operates 7 ex-BA (leased) B767-336ER's - since BA is -36 as someone has already posted (correctly).
so, it's CX B747-467's, B777-267's and B777-367's.
etc, etc, etc.
M88, 722, 732, 733, 734, 73G, 73H, 742, 743, 744, 752, 762, 763, 772, 773, 77W, 320, 332, 333, 345, 388, DH8, SF3 - want