Hi,
As promised an update on fitting senders for oil pressure gauge and idiot light.

I was a bit optimistic thinking I could get a dual sender that would fit between the B20 block and the down pipes. I also learned that 1/8NPT is not a common fitting size, at least here in Australia.

What I ended up doing was getting a thin copper tube set with 1/8NPT fittings at each end that is designed to run a mechanical pressure gauge. This screwed perfectly into the block. I then put a few 3" diameter coils in the pipe to reduce fracture risk from vibration, and ran it forward and up towards one of the PCV rubber hoses. I then fitted it up to a VDO T piece - which is actually straight, with a 1/8NPT tap in the end, and another on one side. The idiot light sender screwed into the end, the pressure gauge sender fitted in the side and I strapped the whole lot to the PCV hose for security. It was then easy to run wiring between the gauges and the two senders. Having the senders mounted on top of the engine has the advantage that the cables are well away from the heat of the exhaust pipes.

All finished, all working.