buying a used 4wd vehicle

Troopy diesels are good reliable vehicles. Grag yourself a trusted mechanic and look for one that's been looked after. 150,000 kms isn't anything for a well maintained model.

The big change in troopies happened later in 1999 when they went from 75series to 78series.

Changes included coil spring front end and longer rear leaf springs, so they had a better ride. Worth getting the later series if its within your price range.

The turbo diesels came out in 2002 and you'd be spending above $35k for one of those.

this is a cut and paste of a cut and pase i have done for simular questions

hzj troopy mid to late 90s is they go for that budget, cant stress enough avoid the ex miners below is a cut and paste from a previos reply of mine
engines are good but can crack heads if overheated. always pays to get them up to operating temp and remove the radiator cap (carefully ) and look for bubbles. get it up to highway speed then take tour foot of the load pedal and let it coast down to 40kph - make sure it doesnt jump out of fith. Look for overdone detailing it could be covering up an EX MINER. poke your fingers in the chassis holes and see if the chasis is full of mud. taste the mud/dust if it tastes salty it is a MINER. prob will use around 13l per100k where a petrol will use around 5l per100k more - do the math (if you can find one) I have just bought an 80 with 200k and it goes just fine. Other thing is just drive it no 2 1hz seem to go the same make sure this one has plenty of go (for a 1hz anyway) Turboeing a 1hz is not recomended as they are not built for it (toyota make significant mods to their turbo motors they are not just the same motor with a turbo attached). Give it a flat out run - anything above 1/2 on the temp gauge spells a problem somewhere. Get the brakes checked they can be chewed out if run in muddy conditions and are often are an unEXpected cost at 1st sevice (if they need work it is a good tool to bargain the price down). After the flat out run leave it idling for 5 min then crawl under liooking for leaks that were steam cleaned (transfer case is a good place to look as are diffs). Take it onto dirt make sure it engages low range easily then do 2 circles on full lock each way listen for the cv joints clicking and any other untoward noises. Check accesories (where fitted work) check springs and hangers for cracks. check shockers after your drive making sure they dont leak (further testing is hard on leaf sprung vehicles) jack up front wheels one at a time checking for play in steering/bearings. check behind the wheels the "ball" the wheel ataches to should be dry or just a light film of grease leaking oil from here is EXpensive.
I have driven plenty of utes of this vintage (same driveline etc) they are very tough and reliable but can break in the suspension/brakes front end areas when used for mining rest is rock solid even when used for mining
I have driven

Do the Transfer case hi and low test. Put it in gear Hi and low and surge it forward ( blip the throttle ) in 1st and reverse to see if the lever jumps out.
Some that have had a PTO winch or other accessories removed and installed on a change over vehicle can be very worn.

Its a bit late to find this out when bogged.

Get the mechanic to take off the timing belt cover and check the belt age. Some people used to press the reset button on the early 90s on the dash.
If this belt fails catastrophic engine damage will occur.

Look under the rubber mats in the back behind the drivers seats, sand will get trapped in bolt low spots this will indicate beach use.
Put your hand down into the jack spot inside the rear body near LH rear door.
In the bottom of the guard you will find dust/mud which will indicate alot of dirt driving, it gets sucked in through the air vent on the outside rear guard.
Also check the water/dust drain on the bottom of the airfliter, its a small bowl held on by clips. Its surprising how many mechanics dont check this. Also a good indicator of conditions driven.