This is the stabilator torque tube (P/N 652-582) which works for the 400 and all twins. Aviall lists for $1,500, yours for $1,000 and shipping. The horn and counterweight are is also for the 400 and all twins, (P/N 22882-003) Aviall lists for $573.79, yours for $450 plus shipping. $1200 if you take the pair.
These were purchased when the first SB came out but where never installed. The owner subsequently sold the airplane so this is part of a few leftovers found while cleaning out the hangar.