...had the manifolds sandblasted locally for $60, and not surprisingly upon close inspection noticed some minor cracks in the outer fins. Didn't appear to be too deep, at least not that I could see naked eye, and in light of trying to prevent further damage I ground out the cracks and cleaned up the channels. I was going to use POR-15 High-Temp exhaust paint, but the same place that blasted also does power coating, including Cerakote (essentially very high temp powder coat), and for just another $60 I opted to give that a try.

Modified the 440's y-pipe with 2" mains to match the manifolds (also the same OE size for a magnum 360). Considering the 'low-rpm' nature of this engine I can't imagine the design of these manifolds will induce any realistic performance limitations, and being center-dump I gain all the clearance I wanted 👍 . All torqued to spec and ready to go -

blasted, showing where the cracks were in the fins -