Rag Joint part# needed.

[65 C20]

I have a Cardone P/S box # 27-7501 which is supossed to fit 68-76 Chev truck. It has a GM or Saginaw #7802644 part # on it. Looking for a rag joint to fit.
I purchased a Dorman #31015 which states should fit varios 73-90 GM's.
It does not want to slid on easy.
I contacted Dorman tech support and they said #31015 is 13/16 ID with 20 spline. They could not cross reference to Cardone.
I contacted Cardone and all they said was that the #27-7501 had 31 splines.
And they could not cross reference to Dorman. I believe they out sorce over seas for tech support. I realise the rag joint doesn't have as many splines but also doesn't spline all the way around.
The box is rebuilt and the rag joint is new. Looks like the spline on box is rounded over slightly, could possibly file splines a bit but since it is rebuilt I don't want to start altering it unless I have to.
Another member said he had a Lares rag joint that just slid on his but I could not get a part# out of him. I am thinking it was a #201 but not sure.
Any help would be appreicated as I would like to do this swap this month.
Thanks Cal.