I'm getting ready to do a batch of series parts and just spoke to the rep for Azz Galvanizing.
They are the closest to me.
Basically, they won't to do a tube or box chassis that is not brand new.
In the past they have had some break in half because of the interior rusting and have concluded that is it rusted on the outside the inside is at least 50% worse......which may be true.
The other parts (including the bulkhead) are no problem
Does anyone have any suggestions?