manifolds

what are these off of?

I wouldn't swear to it, but they kinda look like 340 manifolds. Got a casting number?

looks like small block. thinking 340 as well

If they are off a 340, it's not the early version.
Probably '72-up, that's when the ball flange for the head pipe started.
Any casting numbers on them?

ball flange?

He is referring to the flange where the pipe bolts on. If you notice it is half rounded. The pipe would be flared to mate to it. Post the casting numbers to be sure of application.

318 with the small outlets. Should have smaller exhaust ports too. There are some early A-body 273's that are like that too, but they don't have provisions for heat stove (if that heat stove is really for those). Probably not same outlet angle/placement too as early type too.

here is a pic of my 68 318 manifold. 67 cast date.
Came out of a 68 Fury.
As you can see the ball flange was in use before 72.
I agree the drivers side is most likely for an early a body. Clearance issues would be the reason for the odd exit and the up swept ports.