I never did a 603 type engines head removal. I just assumed the tower bolts also supported the head. Assumptions can be dangerous. Anyways I would not go in that far without removing and internally cleaning plus testing the lifters.

Just replacing those that were testing bad. If any. Also as usual if they had been changed before. Usually the current owner does not get the information to know when this occurred.

As for a rear window area patch of a temporary nature. Perhaps a six mil piece of plastic could be siliconed over the area. The plastic has poor ultra violet resistance. It has never been a selling feature that silicone has a massive amount of uv resistance. It does though.

The only problem is on removal you have to get it all. Nothing I can think of will bond with the residue. There may be another adhesive caulk that is better for something like this. I just do not know what it is.

For us that live in rustbelt areas. The amount of rust established in these series of cars is a really important factor. Easy to repair mechanical issues in comparison. Once corrosion moves past a certain point. It either is not practical to deal with or just not worth the effort.

We did see many cars with far too much of the metal as just iron oxide well on its way to reverting back to nature. Supported on two sides by that insidious coating.

How bad can it be? A neighbor dropped by to use our stretcher and shrinking tools to fabricate a patch for his station wagons rear roof on a ford product. He asked us to have a look at his rear shock towers. A quick inspection was the whole floor was still present but so seriously weakened with rust it was not practical to do anything. You could push a screwdriver through anywhere easily.

His wife was killed in the car a few weeks later when the car folded up. When another car hit it. I really believe the structural weakness of the far too rusted unibody construction was a factor in her death. .

Since then the mandatory yearly initially but now every two year safety checks. Have proven to have some value in stopping this. Some places still give out bogus safety passes. Generally letting minor things pass. They will no longer certify a car with signifigant rust though. There is just no way they could claim in court the rust occurred since the last inspection and might fail their liability issues. Plus have their inspection privliges revoked. A rust hole through the metal anywhere will disqualify a car here.