Id look out for a 525i e34 touring If your going to be towing about a ton. I use my e30 325i touring for towing 750 kgs about twice a month and tow 1 ton about once a month but its more like every weekend lately with m42 owners cracking their sumps. 4WD isnt really necessary Ive seldom got stuck in 5 years towing into and out of wet fields and Ive got an open diff. The times i have got stuck so has everyone else so its just a case of waiting your turn behind the tractor. Also I think self leveling rear suspension was standard on e34 tourings and its brilliant on my e30 touring.