I did a little more research, and Bush Hog offers a unit. Now I am sure there are others too, but this was the one I saw first. I called them, the model they offer for the 600/601 series Ford Tractors is as follows; frame #2346 $3058, mount kit $822, then you need to pick a bucket, joystick and pump. These are list prices they gave me, you could find a better deal.
My 2 cents, makes me think like this. The tractor you have right now is probably worth in the range of, $2500-$3500. Looks like you could spend at least $4500-$5000 on a loader. And you will have a tractor that you will never get even close to getting the money back on. What I did was sell my 640 tractor and get one with a loader on it. You can pick up a nice, say Ford 1710 or 1910, in the neighborhood of $5000 to $8000 with a loader and 4 wheel drive. Or better yet, keep the 641, and get a new tractor anyway!
Kwik Way might have a loader too. Picture attached of what I replaced my 640 with, it is a 85, Ford 1910 4wd loader and backhoe(pic w/o hoe)
Bill