I found a 1955 Gale 5hp at a yard sale
and spent about $120 on parts over the course of 3 years to keep it running. In running condition the old ones are worth about $150 to $200 depending on condition.
I've also maintained old British Seagulls over the years and would not do it again except for a hobby.
If it has sentimental value then keep it. If not, you may be able to get $100 for it tops.
It'll probably need coils or a coil, an impeller and a lot of cleanup if not full carb kit.
Good luck on your decision.