It was close to the weight of one of the bosch blue coils. You cannot use the original mounts, but mine had broken anyway, both on the frame and I had already replaced the clamps more than once.
A little bit of cutting and bashing on the coil had the new coil mounted underneath the 'relay tray' underneath the front of the tank on the right hande side. Near where your front coil is currently mounted.
Half an hour with a hacksaw and a drill. Been there for a few years now. 1979 R65 with point ignition.
I get the impression people don't believe me....Or would prefer to spend lots of $/£ unnecessarily. Contentious, I know.
Steve H