Weird cooling on my 84 D150

All the ideas about water pumps and caps and hoses are fun, and hopefully one of those guesses IS it.

However, being that it has a new radiator and a radiator hose blew off, I'm suspecting it has a weak head gasket or a cracked head. When combustion gasses or air gets in the cooling system, it causes air or steam pockets to form which screws with the gauge and then causes the thermostat to close when it shouldn't. It also pressurizes the cooling system excessively.

Hopefully that ISN'T it, but if thermostat and radiator cap(the #1 most blamed item for any cooling system problem) don't cure it and you have another attack of severe overheating or something blows off again, then you'll have to pressure-test the cooling system or sniff it for combustion gas.