I have done a little reading, so far, I've found that all pre-855,000 guns were pretty much com pletely hand fitted, and fitting would be required for one of those.
My gun is S/N: 371587xxx, which puts it in 1976, and I am getting some mixed signals, "yep, it'll fit, no prob" to "still requires some fitting, 9 times outta 10"
Hope I can find a positive answer.
This may not be a big deal though, the wife is swimming around it like a hungry great white circling a teeny-bopper on a paddle board, so it may become hers, one barrel or two...