I use Lightwave - not cheap, but it can do just about anything imaginable. Wings is respected by Lightwavers and hard to beat at the price..

By the way, Randy, I think you beat the record for reference images - very nice indeed!

Unfortunately, I won't get around to modelling the plow until friday; I'm bogged down in work at the moment (damn Java servers!). Guess which thing I'd rather do..? :(