Welcome to the world of Morris Minors.
I use Penrite HPR30 in my Minor
https://www.classic-oils.net/Penrite-Cl ... erly-HPR30 and in my MG Midget. Engine oil is fine for the carburetor dashpot. Sometimes a light oil is suggested but this can result in the piton rising too quickly when you open the throttle quickly and weakening the mixture, which reduces power. I know the standard gearbox requires 20/50 but I don't have a standard gearbox.
For audio, I have a 30 year old radio cassette in the Midget (It was one of the first where you could remove part of it to make it useless to a thief) and an earlier version of one of these, in the MG V8, which I fitted in 2013 -
https://www.moss-europe.co.uk/retrosoun ... 0-355.html . The workings are very compact and I just leave a memory stick in it. There is a wire, so you can mount the stick elsewhere but mine just rests on the top of the transmission tunnel, behind the radio. The stick has a 4GB capacity and that, it seems, represents a lot of music. Not being one, who follows current trends, I hardly ever remove the stick (Just now and then to add something I have acquired). I will add some thing to the Minor but for that I have an old radio cassette, that came out of another car and was working well (I have only ever actually bought the two systems detailed - all the others came in cars).
Mention of the anti theft device on the radio/cassette has reminded be of a very simple trick for the car. These are very good and a good safety feature when you leave the car (If there is a wiring short circuit, on a permanently live circuit, it will simply blow the fuse that runs in parallel with it) -
https://www.frost.co.uk/battery-cut-out-switch.html . However, it's visible to a thief and easy to overcome. I know of a much better system but I won't detail it here, as it's not only forum members, who can see this. I can let you know directly if you are interested.