There are several aftermarket A/C companies out there that make units specifically designed for our trucks. I too shaved my firewall and will be going with either an OLD AIR unit or a VINTAGE AIR unit (Both OLD AIR and VINTAGE AIR are manufacturers of aftermarket units). I love the shaved look and hate the way the factory heater and especially the A/C looks, like luggage attached to the firewall.
Hope that helps...
Mike