When I started looking for a mog I had a similar thing in my mind. The trouble is although the 404 is a lot cheaper, I decided in the end that it would cost a fair bit to get it doing what I wanted and I'd be better off starting out with a 406. What you hope to do with yours is very similar, so I'd suggest you consider carefully before buying.
The 404 is quite a lightly built mog. I'm not sure how it would appreciate having much weight hanging off of the back of it if you even did manage to get a linkage on there at all. It's a good little off roader to carry light stuff but that's very much restricting your uses for it, and as such it's value to you will be much lower.
How much of a project are you willing to take on? There have been some really cheap 406/416 mogs selling on ebay but they will need work, and lots of it! Or save for a bit longer. The mog market is at a point where you're not really going to lose money on an older machine, so if it doesn't work out for you getting your money back isn't going to be an issue as long as you spend it right in the first place.