Most definitely get all cylinders comptession ch3cked. Leakdown test if
possible. Also, on compression stroke, listen to exhaust, the intake. That
will tell you about valves. Drain oil through a fine paint filter and look
for metal particles. Golen or brass flecks tell about some matertial wear
and silver flecks tell about ring wear and other things. Pass a magnet
through it and see what comes up. Ferrous metal particles will stick. Brass
won't. That will let you separate wear areas. Running the engine using a
listening device against the engine also helps.  Oil analysis over time is
the best way to keep up with wear on an engine. A spike in metal particles
predicts engine or parts failure.

I worked in the oil analysis labratory for the US ARMY at FT Rucker,
Alabama during the Vietnam War. We processed oil samples from main bearing
assemblies on jet powered helicopters,  amd transmissions. We were able to
predict engine or trasmission failure 80% of the tme. Not perfect, but
better than guessing. Especially when the machine was landing or taking off
fully loaded with soldiers. At FT. RUCKER, one dude had the job of hovering
in a sand pit to the point of engine and transmission failure. Our job was
to predict at what operating hour that failure would occur, thus getting
the maximum use from the machine. On that particular project we finally got
up to 88 % accuracy.

Oil analysis is the way to go!

John