I briefly looked into polybushes (we do have them over here too from a variety of manufacturers), but I don't like the fact that they're not bonded and have no outer sleeve. The lack of bonding allows dirt ingress, which then acts as an abrasive. Most of the wear will occur in the polyurethane, but some of the grinding of the dirt will wear the spring and chassis eyes. I was also worried that failure of the pulyurethane would allow the inner steel tube to come into direct contact with the spring or chassis, causing rapid damage to the eye - at least on bonded rubber bushes, failure of the rubber only allows the inner steel tube to rub and wear the outer tube, limiting the damage to the bush. I have seen enough photos of this failure mode to put me off, though I'd buy twin sleeved bonded polybushes tomorrow, if they existed. Interestingly, Tomcat Motorsport and Drew Bowler (the makers of the Land Rover based comp-safari racers) did extensive trials on all the brands and grades of poly and standard rubber bushes in deserts and mud, and found the best handling and longevity by far were provided by the standard Land Rover rubber bushes...:Wow1:
I do have a Salisbury rear axle already, which I rebuilt to have post 1980 hubs and stub axles (so as to match my rebuilt front axle, making sourcing wheel bearings and hub seals very easy, as they're the same as on all Defenders to date) The reason I want later axles are many fold. Firstly, I want disc brakes on all four wheels. Standard parts would give me more confidence int he quality, would be cheaper and a lot easier to source replacements for, especially down-route. Secondly, the steering lock is much tighter on the later CV jointed front axles, vastly reducing the turning circle. Other considerations are the extra track width (having found myself on some worrying side slopes on the Alpine tracks at full load), the elimination of the steering kick-back in 4wd form the CV joints, and the 3.54 diff ratios which my Tdi will pull with ease, allowing the Roverdrive to become a motorway cruising gear (the engine gets a little busy above 60mph, even with all the sound proofing and the Roverdrive, and the 25% gearing increase of the later diffs will help with both noise and fuel consumption).
The rear axle will be relatively easy - I just need to remove the existing suspension brackets and weld on 109 spring seats and damper brackets. I'd like to use the A-frame ball joint on the Defender axle to make up an anti-wrap (anti-tramp) bar, as parabolic springs do tend to suffer a little with Tdi/V8 torque levels.
The front axle is the tricky one, because of the need to set the cator angle accurately and the proximity of the aft mounted track (tie) rod and the leaf springs. The position of the diff being much farther to the right makes life a litle more difficult, too - the side of the diff housing will sit above the right spring, so the right spring seat will need some complex shaping to fit around the diff housing (not just a circular section). This also means the front spring seats need to be deeper than normal for the dif to clear the spring. The plan is to angle the seats a touch and use longer spring shackles, so the axle will be at the normal distance from the chassis and the springs themselves will be the components moved to clear the track rod and diff. I reckon a 1/2 to 3/4" shackle extension, with spring seats 1/4 to 3/8" deeper than normal will do the job perfectly.