But this is what I was checking on, will any of the 4 hole type vintage rail consolettes of this era match the hole spacing on my kick drum shell or were there variations that won't match exactly? And what modern drop-in replacements are currently available on today market?

Just my guess is that a vintage four hole rail mount should match up. But, that's just a guess. You should use a tape measure to determine the spacing on your drum and ask a seller to do the same. I can't offer any information about the modern versions matching up.

Ludwig 4 hole consolettes are pretty plentiful, usually there's at least 2 or 3 of them on ebay at any given time. They all are the same mounting hole pattern so fitment shouldn't be a problem. You'd just have to be careful not to get a MIJ copy as that probably wouldn't fit. Most of those are a two hole design but you never know. Fortunately the Ludwigs have their name stamped on the upright so that's a way to tell. The older "Telephone dial" style don't work as well as the post 1967 ratchet type but are usually a bit easier to find on ebay and somewhat cheaper unless dead mint or something.

Maxwell was repro-ing the 4 hole Ludwig style rail for a while but I don't think those are available anymore.

Ideally I am going to try and source one of the post 1967 ratchet type, 4 hole consolettes at a reasonable price. The holes that remain in my 24" kick drum are spaced at 4" x 2.5" (centre to centre) which is the standard for these tom rails yes?