Proper fitting of a pitman arm on '31 Chrysler 8 steering sector spline

[Gunsmoke]

I've also posted this issue on my '31 Chrysler CD8 Rebuild Diary on WPC site. I need help deciphering the 2 steering arms (aka pitman arms). Both of these pitman arms (Chrysler refers to them as steering arms) came to me as Chrysler arms, and I'm trying to determine just what they are. Both "sort of" fit the spline on the sector shaft for my '31 CD8 steering box, but will not go fully on. The longer, one is 10" and has holes 8" C/C, is 1" thick and goes on spline about 11/16" and is stamped F-20176-1-1 (? Jan '31?). The shorter arm (which came on a '31 Chrysler 8 cyl donor car) is 8.5" long and 6.5" CC, is 1" thick and also goes on spline about 11/16" and is stamped F-21422. Neither of these part/casting numbers matches the steering arms listed in the pre 1934 Chrysler parts list for all Chrysler models. Normally I would expect a pitman arm to go almost fully onto the spline,,i.e. a 1" thick arm would go on about 7/8"-15/16". So thinking these may be for slightly different spline.

 

Can someone check other Mopar models parts list, Dodge etc and tell me if these stamping #'s show up? Or does anyone know the specific details for a CD8 steering arm. Chrysler lists the CD8 steering arm as part # 314607. And, should the arm go on spline almost fully? Thanks.