I would like to know that too. Postal 2 without AWP forever, AVPC, and some other workshop mods is quite barebones.
you know that the latest gog version of Postal 2 does by default come with A Week in Paradise correct?
and clearly if you want mods for the gog version of the game youll need to use the Complete original version from Extras in downloads.
as the offline backup installer version does NOT support steam mods or old mods from what I remember plus it doesnt support MP like the steam version does as well
The AWP that is included in the new version is a shadow of its former self, namely missing levels, minigames, missions and whole weapon packs that the original AWP already had.
I'll tinker with the complete original version as per your instructions, thanks!