Help Identify Early 318 Single Plane Intake

My books go to 74 and end with a 375xxxx numbers. It is probably late 70's manifold. It doesn't have enough ports to be a mid 80's lean burn. Could very well be a truck intake.

Mike,
When was the last year of the 273 ?

Friend of mine was saying that the smaller exit ports on that single plane makes him think it came off 273. That would have to be 66 for it to be off 273, cause it bolts up to the 69-74 318s. What you think ???

Undersized ports big time:
20200620_143038.jpg