Well most Ra4 paper is opaque of course-- Are you thinking about contact printing onto duratrans or something? It might work, but it would be a royal pain and technical quality would not be that great. Unless you have some sort of particular aesthetic in mind I think a trip to the d*****L dark side and printing scans on Ra-4 via lightjet would be the best way to go, unless you want to make Ilfochromes, or have them made.