Yeah, the tow limit of an R31 wagon is not too large, I think around 1000kg..
I have thought about it a bit too, as I need something a bit more practical for carrying my bike and other stuff around next year or so, but an R31 Wagon is really not too viable when I really thought about it..
a) decent wagon (not gutless pinny) seem to be WAY overpriced for their age.. Around $3k at least, if not more. Many dreamers who think they are much newer than they really are, or somehow worth a lot more than they otherwise should be.
B) Not many around last time I looked up.. up here in QLD anyhow. never mind condition.
c) $3k will get you any number of commos, falcons, or likewise wagons with a pretty strong V6 that was built more with towing in mind. Prices on these are much more reasonable, around $3-4k for something 1990 onwards, even sometimes up to 1994, etc. Seems like people have trouble getting rid of them..
So unfortunately, while it might sound like a good idea.. I think the R31 is wagon is poor value for money these days.
But if you can find a well priced one, then you might be in luck