Is your heart set on a conventional loader? If not, try looking at
http://www.Johnnyproducts.com/. He builds dumpable scoops that fit many L&G tractors. I also know that he can make them for a Cat 0 three point hitch, if you have it. I had him build one to put on my ATV with an aftermarket three point hitch. The bucket itself works great, is very well built, and the fit and finish is excellent. The real problem was that my ATV just couldn't deal with that much weight on the hitch (I couldn't get enough weight on the front end to let me steer). If you are looking purely to move material from point A to point B, and can live with a limited lift height, this might be a very economical choice.
I no longer have the URLs, but if you go to yahoo's clubs, there are several L&G ones that talk about loaders, as well as a "home-built" implement one where several people have built them. I think you're going to find the project a bit more expensive than you might think. Unless you already have the hydraulics (pump with enough capacity, cylinders, etc.), you will probably be looking at in excess of $1500.00 in materials to build anything functional. And with the specs you are trying to achieve, probably more.
Try looking for information on John Deere 400 series tractors. JD makes a front-end loader for them, I think it's a model "40", or something like that. When I looked, the going price for them was close to $3,000.00, and the specs aren't up to what you are looking for (I think the lift capacity was only 250lbs). But, it might give you some ideas.
Kevin