My take-
50 years ago- new rim and at least new drive side spokes, complete new nipple set.

today… there is at least one broken spoke, yes? Maybe more torn up, chewed up spokes from the chain?

one thought was new drive side spokes, observing first if the spoke length of the current drive side spokes are good, make notations on what the average length is now.
I would slowly unwind the wheel’s spokes, keep the sides segregated. Drive side are usually 1mm shorter on a 120mm wheel.
with the rim empty, mark the distortion spoke hole to keep track.
push the rim locally back into shape.

Rebuild with that overstressed side to the non drive side- the tension is much lower.
this way your chances of it providing good service for a long time are greatly increased.