Vintage Cars: Thermostat dilemma, engine thermostat, bosch ignition coil

Question
Greets sir

I drive my dad's fiat 131s, 1600cc carburetor, SOHC engine. The engine uses a bosch ignition coil. The engine's in a very bad shape. There's cylinder oil leaking from the bottom of the engine to the ground. It also leaks into the radiator. I'm planning on sending it for quite a major overhaul.
The engine thermostat was removed because it was faulty and no spare was available. Recently, the thermostat housing also started giving problems. Water was leaking, and at one point when i stopped the car, I heard like a frying sound from the radiator because all the water leaked out. There was no spare for the thermostat housing too. My mechanic managed to stop temporarily by tightening the hose on the housing.

Now I've finally got the spare part for the thermostat housing. It comes in a set with the thermostat itself. My mechanic told me that it'll be better to just fix the housing and remove the thermostat because the thermostat only opens up when the engine is at its optimum operating temperature and since my engine is faulty, it may cause it to overheat.. But I thought that it'll be a total waste if i dont fix the thermostat because i finally managed to get it after a long time.

Sir in your opinion, should I get the thermostat fixed or not?
Thank you.

Answer
Since you have a leaking head gasket, it is best to not use the vehicle until that problem is
fixed. If circumstances demand you keep using the vehicle, it is best to keep using a
thermostat--the thermostat actually is a modifier of the engine temperature--not an all
open or all closed device.