They're not making those Gravely's anymore. If it's in good shape you might want to keep it.
I have a bunch of implements I made for my BCS, and a bunch I bought. I don't think a two wheel will do anything a full size tractor with FEL won't do, but a full size tractor is not even going to come close to fitting inside my garden. And it would really tear up my lawn and be way too big for mowing, and dangerous for mowing around my pond. So I really don't have a lot of use for one. I would like to have an FEL for heavy lifting but couldn't justify having one for very limited use like lifting heavy propane tanks. That's why I made the forklift. But if you have a lot of space then you need one.
But your Gravely could come in handy some time.