Putting aside coolant system checks and compression tests, what tests can I do to my newly aquired '91 Carat engine to determine its basic condition and potential remaining life?   Present 127k miles.

What oil pressure should I hope to get with Castrol 20-50 ?

At the moment all is quiet except for a little valve lifter noise which will probably respond to MMO.
No oil light flicker or leaks either.

thanks,  Steve Cotsford