I replaced both my upper bj's when i did my lift and the first one popped off after 3 hits with the fork, the other took 2 evenings of blood, sweat and cursing (now wishing i'd done the lower ones at the same time now

but anyhoo...)
I bought some of the forged ones from machinemart, £5 each and didn't break one.
The fork managed to completly mangle the rubber boot and surrounding metal on the 2nd bj pretty bad. When i hammered the fork in it started to bend the metal lip on the stock upper arm and the arm started moving when i hit so didn't get a good shock from the hit. Tried allsorts to get it to work, heating, 2 forks, super BFOH etc. Answer was to jack up the lower arm so that when the fork was inserted on the upper bj it had good contact with the flat underside of the upperarm. Left the jack in position and hammered and it split after about a minute. If it hadn't seperated on that attempt i think i may very well have been driving around in a fronty with an allover hammerrite finish
You live and learn and that was my first experience of them, wasn't fun! Not looking forward to doing the lowers next time

When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.