That`s not how it works. All of the character`s movesets and physics are a combination of the codeset and the character files. While you may get some attributes of that character when you transfer them over, you can`t completely port the character to brawl and in the end, because of the fact that they are playing on a different engine, they will feel completely different. You won`t be able to do things like DACUS, Wavedash, L-cancel, directional dodging, or other things from the engine. I also find it stupid that you put in some characters, why do you want a slow brawl Marth and a fast Melee-like sonic with completely different physics (EDIT: I am not saying Brawl is bad, I`m just saying it`s slow). Your cast is going to be more unbalanced then they were in Brawl already because all of the Project M characters have had buffs to make them do alot more damage so that matches play more like Melee, so you`ll have your Project M ported characters doing like 10 damage on there weakest attack, while your brawl characters will be doing 3.You saying "I like some project M characters better then their brawl counterparts and vice versa" doesn`t work when they are essentially two completely different games with there own engines, mechanics, and physics.
Also, to answer your original question, it`s a code for the GCT file, you will either need to surf the internet for 5 hours to find it in a standalone form or use the Project M GCT.