here's some pics I have collected over the years; the first one shows the cylinder mount detail if you look closely, seems to be a crude arrangement of keys gripping the cylinder base rim. I would guess that the cases are fly-cut so that the Matchless barrel spigots sit within the top of the cases
this one is a variation on the original theme;
this one, I think, is the original bike as shown in the magazine;
and this is a variant with the flathead enmgine in a Norton frame
they were never popular because the Norton frames were in too much demand for Tritons and TriBSAs!
I also remember a sprinter with a Matchless top end in the early 70s but can't find any pictures of it... I have seen at times, references to similar bikes using Ariel top ends. I have heard rumours that they are unreliable, being overstressed and lacking lubrication ( ie having the same sort of problems as Magnum units ).. I don't know how the top end lubrication supply would work, for one thing, maybe off the chain lubricator and back down the pushrod tubes?
this one I have no idea about except that it appears to be an Indian Scout engine fitted with BMW top ends, so it is presumably a 500cc or 600cc unit, fitted into an Indian vertical-twin chassis