tire size

Got a 1995 1500 truck extended cab stepside. I lowed it 4/6 and just ordered some colored matched 18teens DEEP dish from homeboyz cuz the truck has running boards on it and I wanted the rim and tire to come out to the edge of the skirt not the fender. The question is what tire size should I go with. The factory fenders front and rear have alreadly been trimed. thanks for any suggestions.