Oil pressure switch - wrong thread

[Series2ian]

Hello,

Recently purchased a replacement oil pressure switch for my series2. I believe the engine is a 5 bearing crank early 2 1/4 petrol defender engine. When trying to fit the new switch, it wouldnt screw on. When I checked the thread, they looked slightly different. The part number of the new switch I got is PRC6387.

Thanks
Ian

 

[oxides]

Parts book says the 2 1/4 engine (S3) pressure switch is 90519864