Nice pictures. Looks like you have two nice fixtures.
The history behind these first fluorescent fixtures is interesting to read.
Quite a bit of experimentation was involved by General Electric engineers before the final bulb and ballast design was approved for manufacture and sale in the Summer of 1938.
The idea was to make several different sizes of bulbs and let existing lighting fixture manufactures make the fixture for the new fluorescent bulbs.
Sales of fluorescent lighting really took off by 1940 and fluorescent lighting was widely used in factories during the war.
After the war, food markets, department stores, offices quickly converted over to the new fluorescent lighting as lighting fixture manufactures made fluorescent fixtures for every application there was.
Some of these fixtures were very ornate and even used cut glass and other detailed fittings to attract buyers.
Over the years as newer fluorescent fixtures came along, much of the fancy fixture design was abandoned and a more utilitarian simpler modern design was used.
As a result many of these old ornate fixtures were junked out for a more modern design.
Luckily a few still survive and are sought after by collectors of fluorescent fixtures.
Some of the Lighting gallery members have some very nice examples of early fluorescent fixtures.
Some are restored and some are in their original condition.
Everyone has a different idea of the best way to preserve a bit of lighting history.
I myself have a restored 1940 Mitchell Fleur-o-Ray fluorescent fixture that has become my prized possession.
If you get the old fluorescent light fixture bug, you will soon find your home filled with these old fixtures.
They are quite a conversation piece, look nice and are a practical antique at the same time as they actually do something useful, provide light, as opposed to a antique vase or similar item that just sits there and does nothing.
I would keep the old ballasts and bulb holders, starters as the ballasts can be rebuilt.
Most ballasts and bulbs made before 1950 are collectors items.
Several LG members rebuild these old ballasts back to their original condition and can even make new labels for them. I have repaired several broken bulb holders and they work just fine.
There are some members here that are into your particular fixture, but they are not always here online, but do stop in from time to time.
Be sure to check back and also if you hang your fixture, please post a picture.

I hope your new ballasts are for the T12 bulb as this is the correct size bulb for your fixture if you used the correct height new bulb holders that will work with the T12 bulbs.
The newer T8 bulbs will fit, but will look a little odd and not like the original bulbs if that is what you are looking for.