Nothing back from OP yet on application but I also wonder whether this is a geared link type chain set or a double roller set? The geared link usually last longer but not by enough to worry about it. Double roller chains run smoother and with less noise.
Having been around chains a good bit for all sorts of drives, it's not uncommon to have some slack in a chain drive. If it has less than 1/4 inch of slack in a mid point check then it should have no trouble doing it's job without timing wander. If timing wanders at idle speed while watching with a timing light then it has too much slack.
If some shop did a bad align bore job, it could be a cause but most machine shops set there tooling up correctly to make it straighter and better and not worse. They generally shorten the caps on the mains so that they can stay on center and not affect the diameter by much but oversize main outer shells are available if it has to go oversize. It still should be on center. That's the whole point of align boring.
This is a very good link.
https://www.diyford.com/ford-fe-engi...ltimate-guide/