Changing the ring gear cause mine is stuffed. Got a 2nd hand one for free but has a little wear on a few teeth. Can the ring gear be turned over to use the unused side of it or do they only go on 1 way?

Only go on 1 way with a Lucas starter. The pinion needs the chamfered side to engage.
And, you won't get it off without stuffing it, they are shrunk on. Need to be cut through to remove.

Either buy a new one $50 or so, or fit a Gemini starter motor. These mesh in from the engine side, and don't need a lead-in on the teeth. The ring gear wear you have won't bother it. More reliable starter too (Hitachi).

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Prob is I bought a new mini starter not long ago so not really wanting to change coz I spent a couple hundred in it. The starter does have a chamferred gear

I got the old one off pretty easy just a few hits and it popped off

Hope it hasn't damaged or cracked the cast iron flywheel doing that.

To fit, heat it to a dark straw colour (NOT blue!) on a couple of bricks, using oxy or a BIG LPG burner. Then drop it onto the cold flywheel and let it cool. It will shrink and grab the flywheel.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

You shouldnt be able to tap it off as is heat shrunk on as Kev mentioned

Bin the flywheel and find a good second hand one would be your safest bet.