This is possible, but it doesn't seem to be a realistic choice:

- This would require a great deal of labor, including transporting a large an unwieldy item down the road.

- You'd still have to install new pool plumbing, heating, pool deck at the new house.

- It's all well and good to say, "The new homeowner will fill in the hole", but if that new owner is financing, the bank's going to demand that it's done before closing -- and that means you.

- And when you're done, you'd have a 50-year old pool.

Chances are a 40+ year old fiberglass pool will crack and break sometime during the removal and installation process; my guess is that you won't find a contractor that would ever consider doing such a job. IMO, you will be money ahead, and have some sort of guarantee, if you install new.