I posed the question here since so many have done restorations on these old trucks, I really don't know if I should do it or not. I actually have several cans of undercoat I got at some point from Eastwoods. I am thinking it might be good to protect from gravel damage under the fenders like what you are talking about. I think these inner fenders actually had some undercoat from way back in places. I used diesel fuel to get it off, there was also a good amount of old tar too. I'm still thinking on this.
Steve