BSP is the correct, although I can't remember exact what it is. I believe it's 1/8-27 BSP. I do know it's the same for Toyotas and Honda.

Here's how you can use both the idiot light and an aftermarket gauge. Works great. Put your new sending unit in place of the old idiot light sending unit. Then run a wire from the new sending unit your aftermarket gauge.

Find the little alternative oil port plug that is located inside the passenger motor mount. Assuming it's a 22R motor. Because the 22R has two alternative places to bolt motor mounts, they had to include an alternative oil pressure port. It currently has a screw in plug. Unscrew that plug. Your stock idiot light will just fit inside the motor mount, because it's fairly small. Then mount the stock wire to the stock idiot light sensor.

Larger aftermarket sensors will likely not fit inside the motor mount, so that why it's probably easier to relocate the idiot light sender there.

It's a good idea to have the idiot light, because it's a hellava lot more noticable that a gauge is.

If you have a V-6, I'm not sure if they have the extra port. In that case, you'll need to use 4Crawler's idea of getting a dual unit sensor. I used one of these on my Honda and works great, but they are kind of spendy.