Okay, I'm back. Thanks for all your replies.
Andy - Good points. The master cylinder and dual discs are from the Cagiva, so they belong together. The calipers are shimmed to center them on the disc per Cagiva shop manual
DM - Right, there's a small allen screw to adjust the pushpin to the piston. The free play I have begins at the pushing of the piston. Right now it has 1-3/4 inches at the ball end (when pushing the piston), that leaves 2-1/2 inches with hydraulic pressure. When reaching this point the hydraulic pressure feels quite firm.
Irsih - Drum brakes would have been simpler, that's for sure. I could have opted for one of those 4 shoe jobs (the Benelli Tornado has 2 shoes per side, I think). But then I wouldn't have alloy wheels. There was some compromise here, for sure. But I don't think even affordable drum brakes would have cost me less - I would have needed spokes and (alloy) rims.
Quinten - So as above, yes, the master belongs with the dual discs. The rear brake is also from the same donor bike. I don't know the diameters offhand but they are a matched set and should work well.
So, these questions having been dealt with, is the 1-3/4 free play at the lever end too much or normal? It is certainly possible that I may not have got all the air out of the system - even though the lever feels firm after the free play.
Following is a photo of the forks - all Cagiva except the steering stem, damper and headlight brackets. Trees, forks, sliders and even the fender are from the Cagiva.