I've got it set at 11.5" at the moment, whicjh is the same as a rigid framed (long case) Triumph primary, centre to centre. I am just off the phone to Tony Hayward and he will supply me alloy frnt pulleys with just pilot holes, ranging from 24 tooth to 30 tooth, and can do belts up to 105 tooth 101 tooth being standard long case Triumph.
So I'm off down to the workshop to count teeth
as for centreing the other way (side to side) the pulleys seem to line up, by eye, ok, once I have the mounts welded in to the frame I will be able to space the gearbox to suit the final drive chain correctly, then set up the front pulley to suit the gearbox one. It looks as though it will simply be a case of turning the triplex teeth off a standard Scout front pulley on the lathe and turning the Hayward front pulley down to give a good fit at the right spacing.