I'm not positive, but I don't think the 14-0890-5R UCA will work with a B-body spindle. Your best bet is to call UB Machine and ask Randy.
As for being happy with the arms...it's still too soon to tell. I will say though that, at least in my case, they weren't a perfect fit. As indicated, for the left side, neither 5R or 6L arm fit as well as I liked. I really needed something in between the two. UB Machine could have custom made something for me I'm sure, but... It also would have been nice if the ball joint mounting plate of the UCA was at an angle to the tubes so that the ball joint stud would be perpindicular to the spindle mount when the car is resting on its own weight and the wheels pointing straight forward. With these UCAs, that's not the case. It doesn't seem to be a problem, but I'd prefer them to be true vertical and perpindicular to the spindle.