If the engine is reliable and not blowing smoke or doing anything bad, id stick with it till after the trip as it is a proven motor and known to be reliable.
Anywho, im the other guy going along on this trip! Just bought my 2002 Outback limited yesterday from a fella in Sydney (picking it up in 2 weeks, road trip back to WA!

) which will be the vehicle used in this trip.
The main trek through the outback is through "The Outback Way" from Uluru to laverton WA. There are other smaller treks but thats the longest stretch.
I will be removing the rear seats and building a false floor with sections, maybe drawers, something that wont interfere with the spare wheel well while still maintaining usable space. I have 2x 20l water jerry cans which i intend on putting inside the car below the false floor behind the front seats. I also have 4x steel fuel cans, the roof rack im putting on is coming off my Falcon (which im selling!) which is done up for touring (has 2 jerry can holders already). Not sure how many fuel cans to take but i can fit four up there easy, spare tyres also probably going up there, depends what i fit inside the car. Do wanna keep the bulk of the weight down low.
I like to travel as light at possible, having gone across the nullabor several times and have done a trip to the Alice from Sydney via everywhere else a few years ago, havent had any issues with not having anything i needed nor any car trouble haha. Do keep a box with cable ties, tape, gaffa tape, rope, ratchet tie downs, 4wd recovery kit, hand light and such things.
Roof rack, bash plate, UHF and lights will be installed soon after i pickup the car, bullbar, upgraded shocks (i aim for Koni's) wearing King springs and a 30mm strut lift will be on the cards and the false floor rear sectioning thing. Apart from that, tyres and a service incl full checkover! Will be doing other minor bits n bobs but thats the jist of it. We will probably pool money for a SPOT beacon.
Simple thing driving through the outback, the planning is so time consuming haha.
Are HF radios any good? Do we need one?