Anyone have any advise as to what the best product is to treat the inside of the frame?  Something to kill or neutralize any rust before i paint the rest and start going back together?

The Eastwood brand has a product called POR-15.  Paint on rust. You can use it to paint over rust and it will stop the process.  It is best to clean off as much rust as possible before applying. I also suggest that you put it on with a brush or rag as the fumes are horrendus if sprayed on.

Thanks for the info.  I have the frame blasted externally, so rust is not an issue there.  It is the inside of the frame that I want to neutralize.  So it won't rust from the inside out.  I am told that there is a product that can be applied inside the frame using a chemical sprayer that will do exactly what you are saying, so I am guessing that this can be applied accordingly.  Will have to read up on it and see.

Yes try a product called Rust Mort. You can spry it and it will neutralize the rust.

I just sprayed front end parts with POR-15. I thought it was a difficult to use because of the mixing of the paint. I had to stir forever to get it mixed up good and then the gun would clog as I would move parts from the booth to hang for drying. If I were to do it over I would brush it on instead. It does cover well!

The problem is not the outside, I am blasting the outside of the frame. I know that I can have it dipped, but I still need to coat it with something for prevention.  From past projects I know that even dipping does not kill it all, it just exposes fresh metal.  I want to treat the inside of the frame as best as I can, because they dont rust from the outside in.  It is from the inside out, due to drain holes clogging with dirt. And most people already know that they are notorious for it.  I already have one rusted out cheese grater victim of a frame.  But I knew that when I started.  I am hoping to prevent it from happening again.  So I am looking to do some preventive treatment.  I know I cannot insure 100% that it will not happen, but I am willing to give it an extra effort.  Having to do a frame off rebuild more than once of the same car, due to the same issues, is not my idea of time and money well spent.   Plus, I am building two cars, so I am seriously looking to do what I can to only have to do it once.

Chances: I've never done a restoration and I don't know how "stripped" your frame is, but is there a way you could coat (by pouring in a rust inhibitor) the inside of the frame and manipulate the frame by flipping and rolling, to get the whole inside coated? Surely not a 100% guarantee of a full coat, but an idea anyway...??? -Trey

At this point My replacement frame is totally  stripped.  What you suggest might just be the ticket.  What ever I do it is the project for the holiday weekend so that I can start going back together with the suspension and be able to roll it around.  I am determined to get that stage done before I make final engine decisions.

Good Luck on the 69 Mike.  I lived in Ft Worth for ten years, back in WI now.  Love to see pics of your process.