I have a Flaming River shaft that has 3/4 no spline on the upper end, and 3/4 30 spline on the lower end. It came off my old conversion. I did have to carefully cut the upper end off the coluum since it was welded on by Warden's back in the day. Still, it's perfectly usable.
Just be sure the box end is really 3/4 X 30. Most of the common Saginaw boxes are 13/16 X 36. The old style conversions used a spud shaft that was 13/16 X36 on one end and 3/4 X 30 on the other. If you want my old steering shaft, I'll throw in the spud shaft.
I ended up switch to all Spicer u-joints during my rebuild.
Send me a PM if you want pics or want to talk price.