Less than 50 960 / V90 wagons were imported by Volvo to Australia, making them quite rare here.
I also have one, and wouldn't be taking mine off road. [*]
If you want something of exactly the same size to take off-road or exploring along unseen rough roads, you might be better going with a 940 Turbo wagon. They have a conventional live rear axle and 4 coil springs, which makes raising the ride height far easier, and there's a very wide variety of spring and shock/strut options available off the shelf.
OTOH, the range of suspension components available off the shelf for 95+ 960s and S-V90 vehicles is quite limited. 940 and 960 95+ front and rear suspensions are completely different from each other.
IRS1 (with coil springs) was used for 8 year models (88-94); OTOH, IRS2 (fibreglass leaf) was only used for 4 (95-98), so the IRS1 Nivomat conversion kit with different rear coil springs isn't a direct fit.
If your 965 has Nivomat shocks at the rear, they're probably long past their use-by date. Likewise, the front strut/shocks, if they're original. Monroe struts are presently (AFAIK) the only available front strut option available off the shelf. IIRC, there's only Sachs and Monroes rear shocks available off the shelf for IRS2.
It's also likely your front lower control arm bushes are shot; these wear excessively quickly on these cars. The least expensive repair option with the latter is to replace the front lower controls arms as complete units, then retain the old arms, and rebush them yourself while out of the car so your workshop of choice can replace them as complete units when the bushes in the new arms eventually chew themselves out. When I had get mine done, I found the price of a pair of new replacement arms is not much more than a complete set of replacement bushes, and as the workshop would have to charge me time to replace the bushes in the old arms.....
The 940T might be a better solution in your case, since doing custom mods to add raised coil springs to the IRS2 and reworking a pair of 850 struts to fit the 960 front end isn't going to be cheap.
FWIW, new Monroe struts, new Sachs rear shocks, new front lower control arms with fresh bushes, and new front sway bar links totally transformed the 965 I bought with 238K km on it - it didn't feel as floaty and boaty afterwards. It still feels quite soft compared to my 945T, but that is its nature.
[*] Even if the head gasket wasn't blown....