Probably killed off by smog laws.
I had a Ford F-150 with the 300 cubic inch in-line 6 that was as tough as a tractor.
Yep, all the good old iron I-6 motors are dead. Love the 4.0
in my Wrangler. Good thing it only has 198,000 on it, so
it's barely broke in.
It was originally intended to be an industrial motor but Ford decided to put it in trucks.
And I had an emissions waiver for mine because it didn't pass the sniff test since it was new