Does he have them with the proper offset for A-body brakes now? Last time I checked (a good while back) all his axles required you change to the wider brakes. Have you read his article on "green bearings"? He brings up some real interesting points
I don't know if he has the small bolt pattern axles with the a-body offset. Since the op was asking about BBP axles I assumed he was switching over. I can't see spending that much money on axles and keeping the SBP and SBP brakes, given how hard it's getting to find parts for them.
I have read his article on the green bearings. He does bring up some good points, the tapered bearings do have drawbacks. But even the upgraded green bearing are not as strong as the tapered bearings. The fact that they're used on other cars is of little consequence to me, there are a lot of designs in use out there, it doesn't mean they're better. The thrust blocks are a pain (especially if you forget to install them!!!) but if you're running stock 3rd members removing the block doesn't make them stronger. And since I don't submerge my axles in lakes, I'm not too worried about the seals. So far, I haven't had an issue with spline engagement either. And I have a set of Cass' BBP axles in my EL5 GT with tapered bearings and 11x2.5" brakes.
Everything is a trade off one way or another, I still prefer the tapered bearings. But that's just my opinion and preference.