I'm trying to replace the existing electronic oil pressure sending unit on my '96 Celica with a mechanical one. I have everything in place except the sending unit on the engine block. I can't seem to find a fitting that will correctly match the size and thread pattern of the existing switch. Has anyone experienced this problem before or have advice on what size fitting to use? The engine is a 7A-FE 1.8L if that's any help. Thanks.

-Joe