Hi All- I'm new here, but by no means a 'newbie' to wrenching. Former mechanic- and own a few antique vehicles. I recently acquired a 79 Midget. Loved them all my life, as well as most other old cars. Had a chance once to buy two abandoned Triumph TR4 semi-basket cases (a pair) for like $400, but didn't have any moola back then. Still don't have much...haha. Anyway, I ran into an interesting thing today. The car is in great shape - said to have had a newly rebuilt Spitfire engine installed (I haven't ran the numbers yet, haven't researched even where they are), but the engine bay looks exquisite! Anyway, the oil pressure light comes on at idle, and of course goes away when throttling up. I purchased a little mechanical Sun Pro oil pressure gauge kit to put on so I can monitor the actual pressure. I want to 'T' from the existing engine block port to then service both the original oil pressure switch for the dash light and also the new mechanical gauge. So I went to Napa, and based on their replacement oil pressure switch, the engine block port is supposed to have metric 10mm X 1.0 pitch threading, which doesn't play at all with the US NPT brass fittings. Well, I just tried the 1/8" NPT adapter that came with the gauge and it fits perfectly into the block! Not sure if the block was re-threaded upon rebuild or what. If so, now I'm wondering if the oil pressure switch that is in there isn't OEM. Anyway, this is an odd experience. I've dug into the forums here and learned that others have done the same, but with little more information. Has this block been re-threaded you think? Or, is it really OEM a 1/8" US NPT threading? 79 Midget, Spitfire 1500, year unknown. thx- r.