Crankset looks like stronglight or nervar cottered.
This means that a new bottom bracket will demand a new cotterless
crank. You are better off trying to find a cotterless spindle to put
into your old french cups, get a $10 sugino maxy on ebay, they show
up all the time.
I can see by looking at the teeth that they are still in fine shape.
Unfortunately, it would probably cost $50 to get the entire chainwheel
rechromed. meanwhile, use brass wool and/or aluminum foil to remove
the rust and then wax the crank, if you want to reuse the crank.
good luck.
- Don Gillies
San Diego, CA