Timing chain at 200K, they stretch over time and get sloppy. About
that time the cam shift can be wearing down as well.
My brother special order a new 1978 Chevy Pick-up with the last of the
four-bolt main 350's. He has 300K on it. Cyl. pressure test is still
in the factory range. But, has replaced the chain, cam-shift, AC,
water pump, distributor, carborator, heater core, clutch. But, the
heads never have left the block and the 4 speed manual trans and rear
are still going strong. Yes, front suspension rebuilt twice.
Drive it nice. Take care.