loosing the will to live...

[Rusty]

What grade oil are you running?

[Monkeymagic]

Two easy checks.
Use a mechanical oil pressure tester rather than rely on gauge. I suspect wiring fault
sniffer test for evidence of exhaust gas in header tank. I suspect air lock.

[Rikki Kitto]

I had something similar after an engine transplant, turned out to be the MFTS scared the life out of me

[220bhp]

Thermostat the wrong way round maybe, or stuck. Oil pressure switch on the side of the block . Had that with my rebuilt engine when I fitted it. Only had one bar of pressure on the gauge. New one fixed that. Did you check the head for corrosion around the waterways. these heads can suffer from that if the wrong antifreeze has been used in a previous life.
As all above have said check the obvious things first , because in your state of mind you will always be thinking worst scenario. Bleeding the system on some cars can be a Bar**ed. I cut the bottom of the g12+ bottle and push the cap end into the header tank
It should be a tight fit. Then fill it from there. Works for me. If the bleed nipple on the heater hose wont work, undo the hose and let the air out from there.
As for the steam from the exhaust most cars will do it in this colder weather.
Before you do this check the thermostat. Good luck: thumbs: