I replaced my uni joint about 15 years ago with a Hardy Spicer part.
I can't remember the part number, and my bike is a 81 R100 RS so a different part to yours no doubt.
Easy to cross reference once you have measured cap diametre and cross dimension.
Is your uni peened in place?
I used a steel washer over each cap. The washer was a perfect fit diametre, and also sat perfectly flush with the outside of the yokes, so centreing the new uni was easy.
Two quick hits of mig per washer.
That was a lot of years, and abuse ago.
Lord of the Bings