Along similar lines for me, I think.
I'd be stripping it firstly to assess the state of the internals and see what parts would be required.
If you were going to lengthen the stroke (from the standard 65mm), Mick would usually advise obtaining a piston from a later synthetic sealed gun. The piston is slightly different, giving the longer stroke. However, you may then need to sleeve the transfer port down to get things singing in harmony. We're talking using this later piston complete with the synthetic seal here.
If the original leather seal was there and in good condition, I'd be reconditioning that with neatsfoot oil. Clean everything up. Get a spring with matching top hat and guide from Tinbum. Wire wool, oil, cloths and judicious elbow grease to just clean the externals. And leave be. Nice to have it original and with patina and bestows that nostalgic feeling. Leather seals available now from Protek if it were goosed, or you might at that point decide to go for the newer piston & seal.
Now, if you have other scoped guns, I'd be going along the lines of trying to obtain some open sights and shooting it thus, reinforcing those classic feelings. Protek (and others) often have used sights for sale, or you could try posting here.