Make sure it's not off a wreck with a sudden prop stoppage/strike
Overhauled 1979- 36 years ago! Where has it been sitting all that time? Were the cyls older TCM with the 24 degree timing turn back?
And how many times were they reworked?
$5500 may seem like a bargain, priced exactly to get a quick sale...
Sometimes an engine is pulled off a plane, some guy buys it for his homebuilt kit that never gets built, then sells it to someone else, and so on, and after 30+ years nobody knows the original history and the engine suddenly becomes valuable based on what the "logbooks" say.....
Ask questions! You may open engine and find the last overhaul was barely in tolerances....or has a bent crank, or is all corroded/rusty due to poor storage...
Just sayin"...