Oil pressure is probably abit unnecessary. You have an idiot light for that, same with charge warning light
Oil preassure light sender's are too late... most run around 3psi ( a few have been known to be less)
Atleast with a preasure gauge if it starts to get to the stage of less than 10-15..... i would be looking at maybe its too hot or not enough oil.
VDO still seem to be the best.... just replaced Oil preassure,Fuel, Oil Temp and Volts. ( went for Volts instead of Amps because i was told by my Autoleck that your using Amps to run the gauge)
Just over 300 bucks with senders.
New VDO speedo's are all Eletric now... they are around $240
But u will need the impulse unit and for most early VW's its around $220
Its screws onto the end of the cable.
VDO also do Cylnder head temp if you want to know how hot its realy running.
Tazz