I sold the Ashtabula forks, stem and cranks (which I was told are forged, not cast) for $350+ shipping to an overseas buyer. I gave him the rest of the bike with it. Unfortunately, Pitney Bose (ebays 4th party shipping partner) absorbed it (ALL OF IT, claiming the shock cant be sent overseas)...
I have the same frame (and shock) but a cast iron fork and steering stem, with "ASHTABULA" cast into them. It had no pedals or seat when I got it.
I'm glad I found your pic! It confirmed what I thought the C-chsnnel with 3 holes was for, at the back of the seat tube.
PS: At almost 50 years...