Ed writes:

The lights are made with a long cord to reach to a junction box.

I have those same old lights. They just have a tube going through the niche
for the cord, which tube is caulked with (these days) 3M 5200 polyurethane
to make it watertight. I know this because it was the source of a pesky
leak for years until I discovered it (see http://www.truetex.com/pool.htm
near the end). So you could certainly run new wire if that is all you need,
and retrofit it into the old niches and lights. They seem to be
bulletproof stainless construction; a shame to waste them.