Alan first let me say that I think the fact you want to restore old items for use instead of making them museum pieces is great.
I never really understood restoring things to a point where they need to be placed in a display case.
Now that aside unless you can have the receiver inspected by a professional I would not even consider pressurizing it.
I spent 5 years as a maintenance mechanic and we would regularly see pictures of receivers that let go and the destruction they caused.
A receiver containing a compressed gas is essential a bomb waiting for the inevitable corrosion to weaken the steel to the point it lets go. It is unusual for these tanks to simply start to leak.
One day it is holding pressure the next day it has gone into an earth orbit.
Being the clever guy you seem to be I would bet you could hide a new tank somewhere else still using the old compressor leaving the old tank under it.
Whatever you decide best of luck to you.
Bob
