Need help enabling X-Ray and other mods on a custom server client

I play on a server that that uses a custom client and multiplayer mods. The problem is that I can't figure out how to get some of my mods like x-ray to work with it. I put all the files in the right places but it seems to automatically restore itself to the default files every time I play. If anyone has experience with this sort of thing I'd really appreciate the help. If you need me to upload the client I can do that too or just send you a pm with the link to the client on the server's website.

So, do you mean that the server you play on gives you a special client that you must use? If so, it can be very possible that the server overwrites your client.