*shrug* I'm glad for the original poster that his engine has the good heads, but just 'cause you ain't seen one without, doesn't mean they all came with. I sold my truck a couple years ago, and though it still lives a block away and I still have a key kicking around somewhere, the present owner probably doesn't want me monkeying around under the hood, otherwise I'd invite you over for a beer and a look at those open-chamber heads you think were never installed on roller-cam 318s.
Lacking the truck to convince you to take my word, let's take a look at Chrysler's word; I've attached to this post the relevant pages from the factory parts catalogues for '89 passenger car and '88-'89 truck/van. You can see the expected P/Ns in the passenger car book: 4323 423, which is the head with the '302 casting number, for all 318s except cop-spec 4bbl units. You cannot see 4323 423 in the truck/van book.
Either head selection in the '89 truck and van line was inconsistent, or I had an incredibly scarce one-of-none unit that I let slip through my fingers. :oops: