I'm a little new to the psydex so this might be a really newbish question, but I notice that the only "Possible breeding chain" to get Crunch on Growlithe is listed as Girafarig, however I also notice that Houndoom is compatible with Growlithe, and that Houndoom can learn Crunch as well.

So is this a possible way to get Crunch on a Growlithe?

Yes you can breed a male that knows crunch (or any other pokemon that knows crunch) with a female to get a that knows crunch.

On the psydex it only lists because on all of the breeding chains on the psydex, only the first pokemon in numerical that learns a specific move will be listed.

Oh, that's great. See, I only have Crystal, so I can't catch a Girafarig. Thanks for the good news.