I used to have a C16 with a 1″ fork back in the day.
To be honest, its best left as its designed – either the original rigid, or maybe a 70mm (max) sus fork. I ran ine with a 90mm travel sus fork, and while it was great in a straight line, it didn’t handle brilliantly as the BB ended up quite high, and the whole shape and fit of the bike will be designed around short forks, shortish TT and a long (by todays standards) stem. Built up as it was originally specced, it’ll still be an excellent woodsy singletrack shredder. If I wanted to pimp it, I’d get disc mounts welded on both ends and fit modern tubeless wheels and the biggest front tyre I could and call it a day there.