My experience with hot dip galvanization is that it tends to warp whatever you hot dip unless it is really rigid. The results with chassis of friends of mine were variable, some got warped, some did not. Over here it is difficult to do since the chassis number is stamped in somewhere and the zinc layer makes it unreadable and you are not allowed to redo it yourself, ie. you can throw your car away!

For inside the chassis tubes a wax like product will work fine since it does not matter that stuff sticks to the outer layer, the beauty is that everytime it gets hot in the sun or whatever, the stuff dilutes and crawls into every single spot to seal it. For the outside I can not recommend anything that is tar-ish based like tectyl. It cracks over time and then you get the opposite of protection: water en muck get into the cracks and accelerate the rust process.

I agree that stripping the vehicle to get it done would be a week's worth of work, no rush, just done properly. If you have the option and want to keep the car for a long time go for it

Cheers,
-P