My retired Ag Parts rep (he was an old, old Hy-Cap rep from the 1980's era) told me a different story on how Ag Parts came to be. At the Hy-Cap summer picnic there was a HUGE family fight. This was from a boil over of Hy-Cap doing so much business with AGCO (they supplied them with an A&I like line of general parts at the time) and seemed to be forgetting who/where HY-Cap's business came from (old IH dealer business).
A "line was drawn in the sand" and the company split. Ag Parts started out as a small shell of what Hy-Cap had, but quickly gained ground and (I think in some products like T/A's...... passed HY-Cap). AP Air was created for air conditioning and that took off in sales too!
My rep told me there was a lot of bad blood over those who stayed with Hi-Cap and those who left to go to Ag Parts. (still is I'm told). The dealer I was working for at the time of the split went with Ag Parts. The new Hy Cap rep we got (we called him the Marlboro man cause he smoked so much) was inept at best and hard to work with.