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...different frames and different steels all make for different experiences with opening up the rear dropout distance. I do not know what a drill rod spreader is, nor have I ever watched RJ the bike guy on Youtube. But I know of no early 80's Nishiki frames that cannot be cold set, using the right technique. IN this case, when I say "the right technique", I mean clamping the bare frame in a solidly mounted Bench vise, with aluminum angle soft jaws covering the surfaces, stringing it up to measure how far each side is moving off the centerline, and using some sort of hooked lever arm to bend out each side in its turn. If the right chainstay is dimpled, it will be more resistant to moving out, but it will still go.

Chrome should have nothing to do with this.