Who sells accurate marked/tread WWII style tires for the BSA M20?

email (option): questmasters(at)hotmail(dot)com

No one that I know of now. Unless you can find better in the US? If you go for the original size 325x19. The best compromise is probably the Dunlop K70 universal. A lot of guys are using the Ensign universal, but to my own mind they are a bit too chunky!
https://www.vintagetyres.com/shop/tyres/width-325/diameter-19
If you go for the 350x19 which most guys seem to, you then have the additional option of the Mitas universal H-02.
https://www.vintagetyres.com/shop/tyres/width-350/diameter-19
For years there was an Indian made 325x19 tyre called 'Dunlop Unigrip' which was exact copy of the old Dunlop Universal (fitted here on the front of my experimental Royal Enfield DC)....Perfect! Except that I can't find them anymore as I believe they don't meet the EU road speed required standard?

These modern soft rubber/neoprene tyres require a higher pressure than the originals.....I run mine at 28-30 pounds. Ron

email (option): ronpier@talk21.com

On the tyre pressure front, I run with 25 lbs/in on the front and 30 lbs/in on the rear on all my bikes with excellent results. The tyres are all Avon SM mk2 on the rear and SpeedMaster on the front, very good for my kind of riding.
Richard

I bought the Mitas 3.50/19 and run 25 front and 30 rear at the moment. I am still experimenting with pressures but the tyres seem to work well with the bike.

Not WW2 period correct.
Anyways, I'm thinking that the "Mitas E-07 Dual Sport Front Tire 100/90-19" will be a great perfomer.

I see that "MX1 Canada" has them over here.

That's 4" wide and should be fitted to at least a WM3 and preferably a 2.50" rim....It's likely to steer like a tractor in reverse..will it even fit in ?

The same for me and it run very well ...

email (option): matrot.sandra@neuf.fr

MITAS 3.5

email (option): matrot.sandra@neuf.fr

Norton 16H is around 17psi front, much more than that and it shakes it's it's head violently. The old books warn on this very point

email (option): jeremy@clogmaker.co.uk

I run my 16H on 27 front, 30 rear. No steering damper and just a touch on the rebound. It has never, ever shaken its head...decent forks and spindles though.