Or rebuilt on a warped casing?

What, exactly, fails on the diff? What do you get replaced? The whole casing, or just the innards?

Any decision on this? Curious, have similar dilemma soon, hopefully.

What carburettor? When was the coil last changed? What plugs?

Do you have the repair operations manual?

Doesn't look right to me.

Report back please. Remember the cam rotates at half the speed of the crank, so piston 1 is at top dead centre twice for each rotation of the cam and skew gear.

Rotate by hand the engine one full revolution only and check again.

For any photos of the pulley? Didn't realise they were the same pulley.

Yes, they can.

Convert the "pull to stop" to a series 3 choke cable, use that to activate the glow plug relay.

Valves or rings? Pour oil down the bores and re do the compression test

Engine swaps are common, the engine blocks are physically compatible, so it's possible that it has a new engine somewhere along the way. Or the factory got it wrong..... So long as the log book and the vehicle match, all is good.

It's so marginal. What's your usage? Local or long distance?

Yep, you can get an MOT on an unregistered vehicle. I've two to do so got the guy to double check.