The problem in doing the fronts is the ball joint will probably fail before the bushes, so you will need to replace the whole wishbone anyway, also the polybushes cost slightly more than 2 new wishbones!
Exactly. The front wishbone balljoint is the weak link in the front suspension, you can powerflex the front arms but once the balljoint goes then you bin the lot. Best to keep everything standard at the front, replace the droplinks when replacing the wishbones, the front anti-rollbar bushes on the TS/JTS actually don't give much trouble either.
One big improvement on the front is fitting an upper strut brace. This is quite inexpensive and fairly straightforward to fit. This gives a huge improvement on all 916 Alfas - front line stability is much improved and turn-in is also sharpened up. Well worth doing.
The rear is where the fun starts. Some pointers:
1) This is not a straightforward job. Recent threads indicate the need for a 10 ton, even a 25 ton press to get the old bushes out of the springpan arms.
2) When you do get them out you have a choice of either going powerflex/polybush (they're all polyurethane bushes) or going for the Mercedes bearings upgrade on the outer springpan bush, and getting an 'unspecified sourced' inner bearing from Alfa Workshop. Either way all will be a huge improvment, so long as the bushes/bearings are fitted correctly.
3) Much has been said about these springpan arms. This is the weak spot of the rear set-up, earlier TS cars have solid bushes, later JTS and V6 cars have the rose-jointed bushes. Whatever you do these arms are the nightmare, but if you upgrade them correctly, the results are excellent.
4) Transverse arms are much easier (three bushes each side, six in total), again old bushes can be tricky to remove but not as bad as the springpans. Powerflex are excellent, the eight years I've had these fitted totally indestructible.
5) Upper wishbones. Unlike the fronts you can powerflex these, if the balljoint goes this section can be replaced (the arm is joined together with two bolts round about the middle of the arm). Someone was being generous at Alfa to do this one.
6) Much has been said about reduction in 'passive rear steering' when uprating the bushes. I haven't experienced this, but I think it's important that all bushes are fitted absolutely correctly for it to work well.
Couple of extra pointers on fitting:
i) Make sure when all old bushes are removed the holes etc are absolutely 100% clean before fitting new bushes.
ii) Make sure all holes/bushes are lubed with copper grease etc before fitting.
iii) If washers are supplied make sure all of these are fitted.
iv) Obviously make sure all bolts etc are torqued correctly.
v) Be ultra careful on the inner springpan arm bush. Space is tight and if you overload this you may break the subframe bracket (unlike the outer springpan bush, which collects support from its neighbour the outer transverse arm bush, the inner bush is 'stand alone').
7) Rear ARB is again ok, the droplinks do wear but not as quickly as the fronts.
Whatever upgrade you do it will be an improvement over the original. The Alfa rose-joints are great but they don't last, and original arms are hyper expensive (springpans are now £300 each).
Needless to say upgrading the springs/dampers will improve things further.
Finally do a 'search' on this topic, literally hundreds of threads on this, the springpan arms being the equivalent of a Friday 13th horror flick............
Hope that helps.