Translating anything into Dungeon Crawl Classics RPG is a pretty easy task, overall, with a few caveats.
(1) Watch Spellcasters: Remember the core rulebook says that NPCs need not play by the same rules as PCs. Even with that in mind, though, you will probably want to re-imagine any spellcasters in the original work.
(2) Watch Tropes: The "weird fantasy" mindset of Appendix N literature, and hence DCC, is very different from the "Mos Eisley Cantina" mindset of WotC D&D and Pathfinder. You will run into ideas in 3.x and later modules, such as armies of dwarven cavalry, elf paladins, gnome clerics, etc., that simply do not fit with DCC (unless you decide that they do, of course). You might need to get imaginative with these, and think about what Appendix N authors would have done instead. In general, you will find far, far fewer of these problems with TSR D&D modules, and the earlier ones cleave closest to the source.
The dwarven cavalry, therefore, may become barbarian tribes, the gnome cleric might become a unique monster or a human, etc.
Watch Treasure: A good standard rule is: Change platinum to gold, change gold to silver, change silver to copper, and reduce any copper to 10% of listed value. You might want to do further reductions. Make most magic into fine items instead, and make most of whatever magic is left unique. Magic items with drawbacks are cooler than ones without (i.e., if the players have to decide whether or not benefit X is worth drawback Y, and they are not always certain, you are offering them an interesting decision, and that is great!).
Add Some Weird: Throw in a couple of things that would not have occurred in a 3.x, 4.x, or Pathfinder module if you can. Give your DCC conversion its own special brand of weirdness....be it due to unique monsters, unique treasures, or unique opportunities (ex. a chance to learn spells, gain a patron, or improve a character in some way).
The really cool thing about DCC is that most of this can be done on the fly. Crawl! has some rules in its magic issue (#3) for easy conversion of OSR spells/casters, that you could probably use as a guideline for later editions as well. The DCC core rulebook has tables to help make humanoids and un-dead unique....use them! For the most part, with a few minor modifications (and most of them descriptive) you can convert any D&D/Pathfinder to DCC. I can do this with a few notes, and standard modifications applied on the fly.
If you have DCC 29: The Adventure Begins, you can pick up DCC 76.5: Well of the Worm while it is possible and you can see directly how I applied these principles to create an official conversion of a Harley Stroh masterpiece. If enough people purchase it, and enough people ask, perhaps Joseph Goodman will commission other conversions............I know I would be happy to do more.
But I also know that, if you give it a shot, you will soon find that it is pretty easy to do yourself.
Give it a try.
(Cross-posted with slight modifications.)