I was thinking the oil drain plug was an SAE bolt thread?

Personally I have no idea. They are still available through Nissan.

10 hours ago, Patcon said:

I was thinking the oil drain plug was an SAE bolt thread?

M16.4 - https://www.rockauto.com/en/moreinfo.php?pk=3270447&cc=1209169&pt=10231&jsn=605

That is approximately 5/8, but I'm not sure

Edited December 15, 2025Dec 15 by SteveJ

2 hours ago, SteveJ said:

M16.4 - https://www.rockauto.com/en/moreinfo.php?pk=3270447&cc=1209169&pt=10231&jsn=605

That is approximately 5/8, but I'm not sure

I believe the OE spec tor the oil drain plug is 3/8 BSPP. The threads on mine measure 16.43mm major diameter, which is at the low end of the BSPP parallel spec, 16.662mm +0/-0.25mm. I don't have a metric 55 degree thread gauge but my 1.3mm 60 deg. thread gauge is very close to the spec pitch of 1.337mm.

https://amesweb.info/screws/bspp-thread-chart-calculator.aspx

Edited December 15, 2025Dec 15 by CanTechZ

Yup, 7/16-20 for the seat belts. M12 is a valid spec as well from some DOT document I found 15 years ago when I was researching aftermarket replacement belts. No idea what manufacturers adopted world wide. Also curious what seat belt threads were used on the various early 60’s datsuns (411, roadsters etc).

The 1/4-28 are on the two Z hood bumper . Craziest thing I’ve ever seen. Must have been supplier determined at the time.

And there is that thread on the valve cover breather and trying to find something that will convert it to AN or NPT to run a catch can hose. Seen infinite discussions about it, what folks did to change it, and even some fitting for RB engines someone found that fits, but still waiting to have the actual size stated.