Other than making sure everything is in good working order;
Use the Marzocchi 35mm yokes with your Betor forks, this is what the works riders used to do back in the day. It tightens up the fork angle and handlebar mounts much better position.
Lose some weight, axles and swinging arm spindle can all be aluminium alloy, rear silencer and front pipe !
Electronic ignition with advance along with a lighter flywheel will pep things up.
Fantic 300 front brake plate.
Lowering footrests and moving back is essential.
Speak to Martin Matthews.