Click on www.vintagebike.co.uk to return to the main VB site.
Assuming the '68 model has an oil pressure switch, that's your starting ppoint.
It will either be 1/8 or 1/4 BSP. You'll need a selection of appropriate brass BSP fittings; including a tee piece to refit the pressure switch.
So there dynamic, appears you're buggered.