Plugging vent holes.....found a solution that works well for us, check these people out.
Aluminum tapered plugs, drill the vent holes before galv'ing and when it comes back from the galvanizer, drive these in with a hammer and finish them off with a sander/grinder.
Bruce Reichelt Enterprises
20160 SW Johnson Street
Aloha, Oregon 97006
ask for Bruce 1-503-879-9085