Yeah that is old. Apparently Santana have good records and are happy to provide build date information if you send them the serial number.
Two brakes from the one lever is dodgy. Most people run the drum brake from a separate thumbie or bar-end shifter. The Magura levers are probably worth something to someone.
The bike is likely pretty heavy (ie > 20 kg) but if it fits is probably worth bringing up to date. Drop bars + bar-ends + Tektro 520 brake levers + v-brakes have all worked for me very nicely.
Gearing probably half-step + granny and a tight cassette, which may be a bit tall in the modern age.
Cranks, derailleurs, wheels sound good.
Personally I love to see this old metal given a new lease of life, used and enjoyed.
Post a picture?