I would definitely epoxy primer before welding together. Although it wasn't done at the factory, and lasted (mostly) 70 years without anything on the interior of the parts.

Chuck's suggestion is a potential solution to future rust, although even without that, it'll likely last your lifetime.


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.