Hey all, just need to know if a 0-100 psi Autometer guage will work with the stock RX7 sender.
And also does anyone know the outputs of some of the senders in the car (like Fuel level, Oil Pressure etc...)

 

Does anybody know what size fitting I need to use so that I can put a mechanical oil pressure gauge. I don't want to tap anything, I just want to screw something into the original oil pressure sender hole.

 

Remove the sender and measure it. Autometer's senders have standard treads instead of metric treads like your stock sender has. You'll have to get an adapter to convert to metric OR get a japanese gauge like greddy, hks, apexi and so on.

 

Well I took out the sender and took it to a local hardware store, the sender fit perfectly into the 1/8th pipe fittings, but I couldn't get the 1/8th ones to fit into the block.

 

Highly unlikely. In nearly all cases you have to use the sender that the gauge is calibrated for.