Vintage dh is a tough market. Bits and pieces will be more available for hoarding if that's what you plan on doing. Marzocchi super T', shivers, monster t' boxer forks etc. Cranks and hubs/wheels. Really not dissimilar from the bmx market.
Late 90's Early 2k DH &Freeride was a pretty small scene. Mostly West coast and western Canada. And those bikes got ridden hard. The unfortunate thing is old dh bikes ride like poo just about anywhere, the trails changed and they aren't the best for the high speed tracks of today. All the freeride rock rolls, skinnies and huck to flats are all gone