HELP! finding correct U-joint

STEERING U-JOINT

1968 barracuda notch
1973 RB 440
727 trans - 8 3/4 rear end
power steering
power brakes (disc front drums rear)
steering box ???? unable to get numbers off of it (tight squeeze)

stock everything -
Okay so the last time i attempted this i tried about two or three different u-joints that didn't work for me to the connection point of the steering box - was using with flaming river steering column i currently have on a stock column and will be using stock column.

So first things first.
the cuppler where the steering column meets the basket (stock u-joint) attachment that connects to the steering box came apart allowing the steering wheel to pull out if pulled on.

Question #1 can i use an after market u-joint with stock steering column and stock steering box?

Question #2 What U-joint am i shopping for?