I am looking at buying a BA XR8 ute, it has done 180,000 kms but it is in good condition and drives real strong. My question is when do these motors need to be looked at or have I got some k's left yet

mate these are long stroke motors they tend to go for a very long time, they are very tuff and capable of putting out a lot of hard work.
but like any motor lack of service will cause alot of wear.

just make sure it has full service warranty and has been serviced atleast every 15,000km...

also might be worth getting a insurance company or mechanic check as they can do a compression test on the motor to see how healthy it is