Heater issues.. right up there with electrical
Sounds like your heater core or hope just the valve,is pooched. The valve is easy to swap out,core a bit more of an issue but do-able. From your photo,I pick up the two hoses for the heater and the vacume hose for the dist. but can't really tell much more. There is a small diameter hose that runs from the heater pipe(a small nipple below the heater conection) around the back of the engine to the intake plenum water jacket. The tank is your overflow for the rad. There will be a hose from there to the rad fill tube.
Did we see pics of your car
If the car is running hot,I'd guess there is air in the system somewhere and after you have the heater sorted you will have to jack the front of the car up and let the rad "burp" the air out, or many will put a garden "T" in the hose that goes from the block to the heater and fill there. If you have air in the system,the thermostat shuts down and won't work till all the air is out. Some drill a small hole in the thermostat to help any air pass..see IAP tech bulletin on this issue.
Have fun
Chris