I've got a steering column mounted Sun on my 70 Roadrunner too, (even came with a black garter to hide the stainless worm drive clamp) but it has a narrower sweep than what I remember having on my old Boss 302 in the 80s/90s.
What would the "period correct" early / mid seventies Sun tach face look like, 270 degree or narrow sweep?
i used the old green line sun (not to be confused with the stewart warner green line) two piece back in the day. starting in the later '60's sun went to a transistorized one piece, blue line, 270 degree sweep.
For a early 70's car, I would look for the original Sun Super Tach and not the Super Tach II. They were the later and what I consider the cheaper replacements of the original Sun Super Tachs.