Jim, I'm not sure what your intentions are when your done (I know....it's NEVER really done...
) building your jeep, but if you're going to go into situations where the inside of the frame is going to end up with mud and debris in it quite often, then perhaps galvanizing is worth it.
If you DO decide to have it dipped, I'd take bbc's advice and have it sandblasted. Actually, I thought that I read once, that places that galvanize can dip the frame into a tank and strip the frame clean (but I'm not absolutely positive on that). It'd be a good question to ask the potential galv. shop before you pay to have it sandblasted.
If you're not going to get crap inside the frame, or, if you can hose it out after an offroad trip, then a good paint job with some sort of internal frame coating would probably suffice. Eastwood has a few choices on that.
When I restored my frame, I cut away two small areas of the front crossmember to leave access openings into the frame, and bolted on the rear crossmember to be able to remove it and have access to the rear openings of the frame. This will (hopefully) allow me to hose out any gobs of stuff that might get in the frame.
I used boiled linseed oil inside my frame, after painting the outside. I used Eastwoods 3-step frame coating on the outside, but your idea of epoxy primer and a good quality paint sounds good.
The boiled linseed oil is great stuff, as far as durability goes, but getting it all around the inside of the frame was the hardest part of my frame restoration! And VERY messy!
Very long story, there. I won't bore you with the details. I finally got it, though! After all I went through, I wouldn't recommend that.
For most of us who are restoring our jeeps, much of the "damage" ( rust, rot, etc.) was caused as a result of the PO's not knowing at the time, what rusting would occur on these jeeps, until it was too late. Plus the fact that we're painting and protecting the surfaces more thoroughly than the factory did. And....we know that we have to maintain the jeep better than the PO's did, especially after all the hard work we've done to them. This should help the jeeps last a pretty long time.
Just my $.02.