torn spring tower - GU - help needed

I would also check where the rear track rod is mounted to the chassis.

I don't have any pics but the ones (5 so far) I've seen repaired have all had the cracks repaired correctly (drilling the ends and then welding, then they've been plated and welded and then they put a piece of heavy wall RHS right across the tops of the towers from one chassis rail to the other.
As yours is a ute it is a relatively easy job to pull the body off, very expensive repair on a wagon.
As has been said check around the panhard mounts as well.
You might also find the brake lines and wiring are damaged although it usually only happens on the wagons as the spring towers crush them against the floor.
It happens to most of them eventually, upgraded suspension that transmits increased shock loads to the towers which can't handle the load and then peel off the chassis.
Some of the ex Telstra utes I've seen after they've been reinforced then break the chassis rails, too much load!

Hi Trol - I have a 4.2 Gu with Polyairs, and repaired a torn rear tower.

You have probably already done a search on this forum, but here are 2 of the articles worth looking at: 48174; 2582;
Gorans reply (thread 2582) summarizes it well. Here is the key part:
"They (polyairs) are not suitable for desert traveling over corrugations and similar extreme conditions. Thing about it for a minute. By fitting them you are preventing the coil of working as designed therefore you are transfering vibration to a next weak point which happens to be chassis. Different rate springs (suspension upgrade) is the only answer if you intend to travel extreme tracks."
Also read the reply immediately after by David (Exploroz team).

Do a google on Polyair cracked chassis - finds website for 4wdmonthly review of 2006 4wd of the year, and also mentions GU chassis weakness.
Even the mighty GU has a weakness - who'ld have thought........................Keith

Give Aaron at ATOC in Melbourne a call, he has been thru this and makes up re-enforced mounts now for this purpose.