Strange sink faucet connections

[fpbear]

I have replaced many sink faucets but this one has me perplexed.

I went to my mom's house to take a look at a broken faucet valve stem. I'd like to swap it out with a new wide spread set, but the faucet looks like it is built into the porcelain of the sink itself! The pop-up is entirely contained within a compartment of the underside of the sink. I have no idea how I would replace the spout or if this is even possible.

Maybe I could just replace the stems and handles but I wonder if the metal tubes from the spout would align properly or be the right size.

I can't replace the sink tub because it is overlaid on its perimeter with a fancy tile job.

Here are some pictures from underneath. It is interesting. The home was built in the 1950s.

[HeyBub]

Double weird.

I'd make the confusion go away by replacing the sink!

Still, it's lasted 50 years...

[Don Young]

every effort to repair the existing faucet even if I had to have a new stem made. Otherwise you will have a major job to retrofit the faucet or replace the sink.

Don Young

[Boden]

A long shot, but I've had very good luck finding old, obsolete repair parts at Teter's Faucet Parts, in Dallas, TX. A phone call and a photo will work. They are very knowledgeable and helpful.

Boden