No taillights, marker lights, park lamps, dash lights

My dad's rig has no taillights, park lamps, dash lights or marker lights. I found a 25 amp fuse blown that was marked Park Lamps. I thought easy I will just replace the fuse and no problem. I replaced the fuse and it blew again as soon as I turned the headlight switch on. The headlights, brake lights, turn signals all work properly but no taillights. I have checked the bulbs and the connections and have found nothing that indicates a short to ground. I have even unhooked the rear lights in the circuit and the front circuits and the fuse still blows. I put a 30 amp fuse in just to see if it would work and it worked for about 30 seconds and then It blew as well. I have done some research and even looked at the light control module circuit board but I could see anything wrong as far as burnt resistors or anything. I also checked the headlight switch but nothing there as well. The headlights come on but the dimmer switch doesn't turn the dash lights on. All of the gauges work I just can't see them at night. I have checked all of the fuse blocks the two under the hood, under the dash, and under the rear seat and everything looks good. Please give me some idea of what I am missing. Thank you.