On my 2002 Spyder CC, I needed to replace my sending unit, since it was reading high. OEM cost was also way high, especially since equivalent VDO units could be had for about 50 dollars.
What I wound up using was:
VDO: 360025 which as all the same features as the one that was in mine. Including the "Idiot Light" sender, which is not connected. Summit Racing sells these, FYI.
The adapter to go from the 18MM Thread on the Engine Block to the 1/8NPT, was found on EBay from a company called Mamba MAMBA Sensor adapter fitting M18x1.5 to 1/8NPT oil water pressure temp About $10.
Was it easy? No. Getting the old one off is challenge. It is torqued on tight! I had read some warnings about using a crow's-foot on the bottom nut in the crowded space with wires and the crank position sensor. So I tried a small chain wrench on the upper body of the sensor. This managed to spin the upper body, but not the lower body. Damn! The nut on the bottom is 25MM. Crowfoot set goes up to 24MM so I had to get a 1" (25.4MM) to use. It worked. I released the wire loop holding the loom that runs next to the sensor so I could make some room to work and I pushed the wires out of the way, as best I could. I got it off without causing any damage. It took all I had with a 1/2" ratchet driver.
I checked the resistance on the old unit after splitting it open and made sure it matched the one I bought. All good. Taped up the 1/8NPT threads (not the 18MM, they come with a copper gasket). New sensor has a 17 MM nut on the bottom.
On test, it went straight to 70PSI and I thought I was having a case of Deja Vu. But as soon as it warmed up and dropped to idle the pressure came down to 35-40PSI, so we have a winner.