Well, we have a nifty little guide for installing mods into San Andreas manually, which is located here.
Please note, that installing clothing is similar to installing a car, only when you get the .txd file, you would place it in player.img, rather than gta3.img.
And many car mods also replace lines in handling.cfg, default.ide, etc..., so just open these files in notepad to change the lines.
I'm gonna have to add pictures to that guide...