I think you could gather the parts for ~$2,500 - I believe "useable" rotors are difficult, or is there a current aftermarket solution?

HEMI Specific; booster, master cylinder, lines & AIR GRABBER bellows
'68-'69 B-body disc brake Specific: spindles, brackets, hoses, calipers, rotors, fasteners

some parts are available aftermarket, rebuilt, or "clone" parts - it just depends how CORRECT you want it