Another powerflex thread!
It's an important one though, and from my experience of trying to get it 'right' on my Spider I would suggest the following:
1) Leave the front alone. As noted the balljoints tend to go first anyway, just keep the wishbones/droplinks fresh and all will be ok. Don't forget to replace antirollbar droplinks every time wishbones are replaced: the rubber bushes compress and are never good if 'reapplied'. You'll get the dreaded 'knocking' otherwise. For the front , use a strutbrace instead. This really firms everything up quite nicely.
2) The rear. So much has been mentioned on this, I've mentioned it
before but for my money's worth I'd suggest:
i) Replace the six bushes on the transverse trailing arms (powerflex
codes PFR1-710/711/712). Make sure the washers supplied are
fitted as these provide important support to the bushes.
ii) Upper wishbone bushes (PFR1-716): I agree, don't bother with
this. Again if anything goes first on these it'll be the balljoint. I
replaced mine but it was a fiddly operation. The balljoints were
quite sloppy so no doubt at some stage they'll need replacing
iii)Springpan bushes (PFR1-713/714). If you have the rose-jointed
springpans, and the joints are ok, leave well alone. All V6s and
the later JTS engines had the rose joints: yours may have them
as well. If not, definitely replace with powerflex. However,
further complications for these bushes are:
a) Make sure when fitting all bushes and especially on these arms
that all the old rubber etc is completely removed and totally
clean before fitting. The fitting of these bushes is also
extremely tight, especially with PFR1-714 as you need to fit a
supporting washer with this.
b) The long bolts/nuts securing the springpan arm to the trailing
arm gets tired with age. The retaining nut becomes less
effective with age and I would highly recommended
replacing the bolts/nuts with new for safety sake. On my
Spider I did not do this on the first fitment and had the
experience of increasing play from the offside springpan.
c) Of the two bushes the inner one (PFR1-713) seems to suffer
more 'wear and tear' than the others. This may be because
it 'stands alone' on the subframe, and also there is no
washer designated for this bush. I have had problems with
this and am going to give the 'Black Grade' bush a go as
soon as I get round to it.
Obviously only other thing make sure you use a specialist who knows what he's doing. The job is tricky, needs some experience, certainly an understanding of how these cars are set up and work. If you get a good job done the transformation is dramatic. Your GTV/Spider is transformed from a sloppy rubbery jelly, endowed with utter cheap and nasty rubber bushes, and is transformed into the car it should have been in the first place: precise, surefooted handling, with unbelievable handling through the bends. Those who own these cars but haven't had the job done, will find such superlatives hard to believe. But when they do experience the upgrade, they'll wonder why on earth they put up with all the substandard specification bushes in the first place.