The timing chain plastic guide rails must be checked. Search the archives here. What happens is a piece will break off and jam in the cam gear. This stalls the chain or makes it skip. Either way, it is a disaster. Less than $10 in parts to fix. When mine were replaced, they were the color of brown glass and even more brittle. The new ones are bone white. The valves can hit the pistons and break off. The cylinder walls are hardened aluminum which work great but can't survive being scratched with valve heads.
Spark plugs are a little hard to get at on the left side. You have aluminum heads which are have delicate spark plug threads. Someone here said that you should work on plugs when the engine is stone cold.
How is the steering? I have had a bunch of work done on the front and still have some wandering. Good tires that are properly balanced are key.

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VR
1967 250SL