https://www.rugbyleagueproject.org/seasons/nswrfl-1975/round-4/western-suburbs-magpies-vs-canterbury/summary.html
In viewing the video, I can see all starting numbers for Wests except for 6 & at 1:59, I can see number 14 scoring a try. Don Rogers was not originally selected, so I am going to say that Rogers is wearing 14 & the other players in the backline kept their original numbers which are: 1. Dorahy, 14. Rogers, 3. Knight, 2. Parker, 5. Mullins, 4. Heyward & 7. Raudonikis.
I can see all starting numbers for Canterbury except 1 & 6. Their backline numbers were: 19. Moseley, 2. Anderson, 3. Ryan, 4. M.Hughes, 5. Gillogly, 17. Winchester & 7. Pickup.
At 1:27 into the video, you can see Winchester in 17. At 0:33, you can see Moseley in 19. You can also see Moseley kicking at goal at 2:07.
https://www.youtube.com/watch?v=Z0e2vO7TqnM
Updated