P.S Kenbo, re: "no compelling reason" to use stainless to fabricate a flange...it wasn't so much concerning seawater...I was presuming a SS exhaust flange wouldn't rot
from ambient air salt
...and would hold up better with heat in case it needed to come apart in the future. But would there be a dissimilar metals issue of different expansion and contraction rates as the engine
and exhaust heated up with use and cooled down at shutdown? Would a SS exhaust have sealing problems or even warping at the flange/manifold joint since the manifold and block are cast iron ? CatalinaDirect's new flange they sell with their custom SS exhaust riser looks like it's iron...I wonder about that expansion issue.
Locally in Jacksonville
, FL it looks like some decent availability of metal stock..."Alro Metals" seems to be national, and even has an eBay presence....with machining services too...and there's others...looks like light at the end of this tunnel.
Thanks again for your specific stock and machining ideas !