I have overhauled (complete..not just top overhaul) both Lycoming and Continental engines.
Overhaul costs for lycomings are always more cost effective than Continental. The difference is really in labour.
Tupac, before you buy find out if it was "Top Overhauled\' or "completely overhauled". There is a difference. Top overhauled engines are basically running new or overhauled cylinders. Completely overhauled engines have been split apart, all steel NDT'd, measured and re-assembled IAW the manufactures specifications.
Also, look at the overhaul or last inspection date of all engine accessories (Mags, starter, generator/alternator, fuel pump, carb or fuel servo etc.)
And lastly, actually first.....Have the aircraft run when it is cold and listen to it. If it runs a bit rough when it is cold and then seems to smooth out once it is warm it has an exhaust valve problem. Don't get snowed there..It should stable-ize out within a minute or so and idle normally. A sticky exhaust valve can eventually seize and cause push rod, lifter and camshaft damage.
just my $0.02 worth, but I have been doing this stuff for over 30 years.
cheers,
RTR