if you reaaaallly want it, it's gonna be an extensive mod, as you would be adding an entire reverb circuitry and tank. This would mean extra holes, extra tube, reverb transformer, more wires and whatnot. Not worth it.
Models which offer reverb as an option but do not currently have it can have it added without a whole lot of trouble. Mesa charges around $200. to add the reverb option. The circuit board and chassis are already set up with holes etc. it's just a matter of adding a tube socket, rca plugs, a potentiometer, the parts and a reverb tank. The reverb circuit is relatively simple.
