I have a 66 833 with the 26 spline output ...that is the smaller output shaft so it's not as tough as the later 4 speed 30 spline output but I am thinking it should hold a mild 360....???
I have had it for years and I wasn't sure what to do with it because when I bought it, I didn't know the difference in output shafts then. I felt kinda screwed over on it, so I might as well use it and hope the 360 doesn't kill it.
You really need to get an education to go to swap meets, people prey on others who don't know what they are looking at yet