For the Avon Speedmaster is it the 3.25-19 or the 3.5-19 for the front tire?
And what sized Dunlop K70's for the rear?
This is the same combination I have on my 1958 Norton. I bought them because they looked 'period correct' (or at least they were after I filed the 'Made in Japan' off the K70). The original rear Avon SM's were notoriously bad. TBH, if it wasn't for the aesthetics I would go for more modern sticky rubber. The Avon tends to find all the grooves in the road and the Dunlop is too hard for my liking.
I run BT45s on my 750F2. Not by choice, they were on there when I bought the bike. I've had them on two bikes now, and the fronts tend to square off very quickly. Best tyres I've used on a 750/4 are Avon Roadrunners or Pirelli Phantoms.