"Who has already replace ALL the rear bushing on a IRS? Is it a hard work? Did it improve the handeling? I can not find the rubber bushings for the traling arm, only red ones. "
I replaced all of the bushings, repacked the CV's, wheel bearings, and replaced the shocks on my 74 super. I found that the fit of the two smaller bushings at the inner pivot point was okay, but the outer urethane spring plate bushings did not fit as well as I had hoped. I would use the rubber bushings there and urethane on the inners.
As for the amount of work....it's a 'friday night' kind of job. However, I would recommend soaking all of the fasteners for the spring plate and the inner pivot bolt(the allen head one) for several days with spray penetrating lube prior to starting work. I soaked mine once a day for an entire week before starting work. Every single fastener came out without a hitch.
Chris