Lower Ball joints.
I have changed hundreds if not thousands of lower ball joints on cars (being a licensed mechanic) and I have never had to do an alignment after. As long as the ball joint has been made to the specifications of OEM, the size and length should be the same. On your Bonneville there are 3 nuts and bolts (or studs if they are OEM, which would need to be torched or ground off) that hold the ball joint onto the lower control arm. The other one is on the top of the ball joint that entends through the control arm. After you get all four of these off you will need a pickle fork to pop the ball joint out. Reverse for installation making sure that the it is tight and greased. As long as you don't touch the 2 bolts on the bottom of the strut (which adjusts camber) or the ones under the hood on top of the strut (which adjusts castor), the alignment will not change. Please use either Moog or OEM front end parts, cheap does not pay!!! If, for some wierd reason, the steering is not quite right after doing this (you will know!!!), then take it in for an alignment. Again, this has never happened to me.
This is just my advise.
1992 Bonneville SSEi
White, grey Leather interior.
Tinted windows and blackouts on headlights.
Custom high flow exhaust, Everything replaceable - DONE
300 000 kms original engine, tranny 2 rebuilds.
Playboy Bunnies Embossed in Tint. Oh Yah!
Ever Seen a Polar Bear in a Snow Storm?