If it really is rust-free and everything is there I think it's definitely worth $350! And if it at least turns over, even better. Pretty much all the mechanical parts that you'd need to get it back on the road are readily available, fairly cheap and pretty easy to install. If you have the time, the space and a bit of $, you'll have it back on the road in no time! As far as an 'investment,' I don't know... Whether it's one that 'pays off' I guess will depend on how cheaply and easily you can get it on the road. Running well and on the road, rust-free and overall in good shape they seem to show up with asking prices anywhere from $1500 to $5000, with the average I've seen around $2500 or so.

I understand the wagon-lust! I have a '66 2-door that I absolutely love, but I'd really love a wagon. Someday.....