These are some notes on running Goodman Games's Castle Whiterock megadungeon adventure (written for D&D 3.5) using GUPRS Dungeon Fantasy or Dungeon Fantasy RPG.
You can buy the Castle Whiterock PDF on DriveThruRPG:
https://www.drivethrurpg.com/product/50947/Dungeon-Crawl-Classics-51-Castle-Whiterock
The cheapest way to acquire enough GURPS to run this is to get the Dungeon Fantasy RPG PDF from Warehouse 23:
http://www.warehouse23.com/products/dungeon-fantasy-roleplaying-game
See https://dfwhiterock.blogspot.com for campaign logs.
Sorry, the Roll20 assets are not available. Too hard to separate out other people's copyrighted tokens and maps.