Only problem is JD didn't build a Model B in a 4 ft size. Must be a customized version. I know for sure because I assembled JD model B drills back in the 60's when I was employed at a JD dealership before I was reincarnated into an old crippled fart.
JD has the seed cups.
BB3592M Tube View/Update 43.06 USD requires cotter pin
BB3607M Tube ADD 29.62 USD
What are you calling the road that drives them? Do you mean rod?
Counter shaft or feed shaft? Feed shaft I'm guessing. FYI the feed shaft is fairly complicated to R&R. What distance are the feed openings apart(center-center) and how many openings on your customized drill?