The most common complaint/problem w/ the 3.0 is headgasket failure. With the weight of this vehicle, I'd guess that it may be even more likely?
There is a factory recall campaign on this, however. Get the VIN number, and find out if it has been addressed already.
There are .30 owners here (not myself) who can be more helpful.

Also, if you still find the 3.0 to be a bit underpowered, the newer 3.4 is a popular "upgrade". if you dig around there are a number of references to this (If yer up to some work/downtime on it of course).

With 200+ Billion electrical parts, the world most complicated machine is inside your own skull.

Question Reality.
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'89 Rnr DLX "SR4.5", 32s w/ 5.29 locked f/r blah blah