1) Mileage = who's to say the #22 head was installed new? Does the block serial number correspond to the car's VIN? Is there a block serial number ahead of the IP or is there a tag on the bell housing flange aft of the block heater?

2) Bolts = the only different bolts are the ones that go into the front cover. Hardware store bolts are fine.

3) Head = a worthwhile machine shop should be able to remove and install the prechambers. Give them a good ultrasonic soaking in case the PO ran WVO. I don't think you can properly surface a head with prechambers in place. Get more opinions but mine is measure the head for flatness then decide if work is needed. Don't touch it beyond a good cleaning unless necessary. An alternative to a thicker head gasket is prechamber shims and living with cam timing that's slightly retarded.

4) Glow plugs = really? Replacing glow plugs in a 603 engine is a clumsy job at best. I'm sure the forum will crowdfund a set of plugs until next payday to save you the hassle of doing it when the head is back in the car. Check the head bolts because most likely they're still within spec to be reused. That'll save you half the cost of a new set of glow plugs. At least check resistance then put the worst ones in positions 4, 5 then 3 in priority order so it'll be easy to replace them by pulling the cruise actuator when you can afford new plugs.

Sixto
MB-less