There is no such mod. I know, I've looked at SC mods all over, and I've been modding the game for over seven years.
The Barracks cannot hold ANY unit what-so-ever. Air units cannot be loaded into anything. The only thing you can change is having the Bunker hold up to eight units.
If you try to edit any other Terran building to hold units, your game will crash and burn. It did for me several times.
Sorry