So what I'm trying to do is make my portal 2 mod read the content files from half life 2 using the gameinfo.txt file, because i have way too much content used to be able to properly pack it into the mod without having a massive jam of 3 default hl2 vpk files packed into the same vpk. I've tried directly copying the part from the half life 2 gameinfo.txt where it references the files into my portal 2 gameinfo.txt, but to no avail.

Any ideas?

The best way around this is to actually grab the stuff you're actually using from hl2 and copy it into your portal 2 folder. You don't want to overburden people's hard drive space and downloads by packing in all kinds of shit you don't use

During development you can turn the HL2 GCFs into a VPK and "install" it as a new DLC.

Yea I've already unloaded all the files I need (basically everything) into portal 2, but the issue is that I don't want to have the player be required to download duplicates of all the half life 2 base game vpk files, or a massive vpk file containing the majority of the half life models, sounds, textures, portal 1 content, and custom files, when they download my mod. I'd rather have it read off of existing files that the player already has.

Believe me, the file would be really big. I'm using a ton of content, plus I'd rather not have the player be able to get all that content free without downloading half life 2, first.

VALVe has said mappers are allowed to distrubute content from the Source SDK Base, so that isn't the problem.

Specially if it's a mod, just pack in the stuff into vpk's.
A few hundred mb's for a mod is always better than a few gigs for the source sdk base. ;D

Alright then, I'll just do a final compile at the end of the mod for all the content.