New cooling system, still overheating.

Never assume a blown head gasket without doing some tests, as suggested above. Get the $15 compression gage kit at Harbor Freight. If 2 adjacent cylinders are low, suspect a breach between them. Connect compressed air to the HF hose (has air fitting) and find where it is going. A leak to the coolant would hiss & bubble at the radiator cap. There are also chemical sniffer kits to test that. One usually gets oil in the coolant if a head gasket leak to coolant. You will see a brown mousse floating at the top. I ran my 82 Aries like that for a few months one summer before junking it. I would fill w/ water each day and could drive 22 mi to work on the interstate. It would boil over each day as I got home, w/ more brown slimy gunk in the coolant.