After my rag joint ripped I ended up adding a Borgeson U-joint at the steering box and I added a Borgeson telescopic shaft (1" DD x 3/4" DD) to my 69 K20. I had previously added a Borgeson U-joint at the steering column.
Here is a pic of the u-joint which is 3/4" x 30 spline and 1" DD to fit the power steering box I'm using which is from about a 1978 Chevy 4x4.
and a pic of it at the steering column - the steering column is not secured yet so ignore the block of wood that has the column wedged in place. That U-joint is 3/4" x 36 spline and 3/4" DD.
The telescopic shaft ended up being about 11 1/2" long but I'm using a van tilt column.