I don't think the 'classic' Seagull paper is still in production - and that which is out there is coveted by anyone who does lith printing.
As it's unlikely we can get G4 Galerie (wonder what the MOQ is to get a batch coated?), other solutions to look at include using the 130 undiluted or other high-contrast developers to bump up a 1/2 to 1 grade. Alternatively if you can get the G3 (also called #3, or Freestyle listed it as G4 I think) version of Kentmere's bromide emulsion, it's more like everyone else's idea of G4-5, & use a softer working developer like Ansco 120 to pull it down a grade. It's out of production but lasts pretty well. Pre & post flashes also help there for different effects depending on need to open shadows, pull down highlights. Post flash can also be dodged & burnt, though it's a bit like flying blind.
Staying in that vein, filtering MG paper with a blue separation filter (or the one you had custom made for ortho effects) would give you the slow emulsion only, eliminating any fast/slow emulsion crossovers you might perceive. Again, you'll likely need a soft working developer, though the pyro stain might actually be beneficial here.
Regarding Dmax, I'd go by look of final print, rather than fetishizing the densitometer. Best prescription is a year of printing only on matte papers - not least as it shows far more about print 'richness' having a lot less to do with Dmax & more about total approach.