I don't know if your install has other problems but to help you eliminate other possibilities, do the following:
Uninstall any F1 79 in the launcher packages section if it shows up there. This should delete the files from the /installed folder.
Close rF2. Open Steam (client, not browser to be safe) to workshop. Click subscribe (unsubscribe first to be safe). When you subscribe, you should see that it is downloading (bottom of steam client should show downloading, you can check out the download manager by clicking). Wait for it to finish before lauching rF2.
Once download is done, check steamapp/workshop/content/365960. Your new files should be there. If not there, something is wrong with your subscribe process. If files are there, start the rF2 launcher. You should see "auto-synching" or words to that effect. If you do not see it, I do not know reason (maybe that also flashes by quickly). Launching rF2 proper should show the vehicles. If not there, I have no idea.
If you want, you can copy the rfcmp file from /content to the /packages folder on the rf2 install folder. Then open rF2 launcher, click on packages. F1 79 should show up (might need refresh list). Select, install. It should say "successful" else error message. If ok, lauch rF2 proper. You should see the vehicle in your list. If not there, I also have no idea.
The other one is verify files integrity on Steam, if nothing else is working.