I'd advise whatever brand you get, get one with 2 lift cylinders. It will give you twice the lifting power, although slower. Not sure what 3 pt. attachment you'll be using to move the dirt & gravel, but sound like fairly heavy loads. A single cylinder unit has the tendency to bend/break the bell crank the cylinder attaches to, or bottom bracket holding the other end. Not from lifting, but from bouncing when moving a heavy load in the lifted position. I've seen several at auctions where they have been repaired, or just still bent.
Approx. 30 years ago I bought a twin cylinder Saginaw brand 3 pt. for my M, mainly to pull my Overland 1-1/2 cu. yd. scraper pictured below. Although it was slow, and at times struggled to pick the fully loaded scraper it never damaged any of the components such as bell crank, lift arms, etc. and I moved a lot of dirt with that little scraper, even with the 100 lb. wheel weight I had to bolt on the side frame to keep the front end down. It was a whole lot more weight on the rear end than the tractor was probably designed to carry. Back then I'm thinking I had around $750 in the set up with hoses & fittings to hook it up.
While the 3 pt. geometry wasn't 100% correct, it worked very well for what I used it for other than the scraper, like 3 pt. blade, etc. You just had to set the top link for the tool you were using. The blade for example worked great in grading position, but looked a little funky when you lifted it up all the way. The top link would push back on the top link connection of the blade, and it would sort of fold under itself some. Nothing that would hurt anything just looked odd compared to a regular 3 pt. tractor.
Just be aware there won't be any down pressure, as it's built into, at least the one I had on the lift mechanism. On the other hand, it was nice because it acted like a float position on many loaders. Nice for finish grading with the blade reversed. The 3 position lever on my M worked very good. Most important if you're going to be moving material is to make sure the "hold" position works well.
The only thing I didn't really care for was removing the original drawbar and frame to mount it. It did have a hole in the lower framework to pull with, but never tried it other than something light. Before mounting the 3 pt. I pulled a 3 bottom pull type plow when our tractor club would have plowing days. It just didn't look substantial enough to pull that plow in a lot of the clay ground we have around here.
