Stephens Trusonic Speakers

I have a pair of Vintage cabinets and inside are 12" Stephens Trusonic (16ohm) woofers with the bronze dust caps, also inside are 8" 18 Sound (8ohm) drivers for the mids. No crossovers built in the boxes. My question is simple, are these worth building crossovers for them and are worth anything now?
They have followers. Check ebay
Stephens Trusonic was my first purchase of audiophile speakers, nearly fifty years ago. They were popular in the fifties and sixties, of excellent quality and very well regarded; similar to JBL but not quite as expensive. Mine were the 8 inch version of yours. They were known as full range drivers with the aluminum dust cap extending the range of the woofer to the mids and partial highs. Your caps must be somewhat dirty, possibly from a smoker's environment. If you decide to try and clean them be very careful because the aluminum is extremely easy to dint. On their own they were very good sounding but were designed for optimal performance to be mated with a Stephens tweeter.

Why your cabinets also have an unknown (at least to me) 8 inch driver does not make much sense, unless they are co-axial with built in tweeters. Even then it's a little 'different'. You'd be better off chucking the 8 inchers and try to find some Stephens tweeters (not very common) or substituting 16 ohm JBL 075 tweeters with an N2600 X-over network (Very Expensive).

So, unless you have a sentimental attachment to the speakers or enjoy tinkering with Vintage Gear, selling the Stephens on ebay to a Stephens enthusiast might be a better choice. Good luck with what ever you do.
I had a friend, Robert Allen from Altadena, California, build a beautiful 3-way system employing the 120Fr for the woofer, the 80 fr for the midrange, and I went over to Culver City (this was 1968) and purchased a pair of toroid tweeters.  He made a folded corner horn for the woofer and a separate horn enclosure for the midrange with the tweeter at the mouth of the horn.  Had those speakers for 20 years and deeply regret loaning them to my twin brother, who managed to trash them.
Robert built a folded horn enclosure for the 15" Trusonic with a JBLcrossover -- the same one used on the Paragon.  To this day, this was the  finest speaker I have ever heard.  Robert knew how to get the most out of those trusonics.  I see your request for advice is two years old.  I hope you kept those speakers and added a tweeter with a good crossover.  You can't go wrong, IMO.