1980 lull 644

I am looking to purchase a 1980 lull 644 gas job motor. The machine itself is in fair condition. It does need some work like a new master cylinder, a couple of leaking hoses. Tires are weather checked but about 50 percent good. It's also a gas job motor. Would anyone know what a fair price for this machine would be? The paint is still in fair condition also. Thanks