[Getter-Done]

In the 80's they made some bolts with metric threads and a Standard wrench size hex.
They done this because of the production line process.
And also the vendors that parts came from played a role in this.

I just found this to be true on my 208-transfer case I am working on.
In the reverse order /metric head with standard threads.
Metric socket and 3/8-16 TPI threads.

Working at a Automotive plant for years I learned a lot about this.

They have to set up each job station in the assembly line
So the technician works efficiently.
So in the 80's the engine components were standard and under hood stuff was metric.

The technician would use one air gun too shoot 20 bolts in a minutes time.