I wouldn't open the 273 up yet, if it was idled around by a retired couple, and not many miles put on it in the last few years it may just have a stuck ring or two. maybe do a oil change with some rotella 15w /40 and add a quart of marvel mystery oil to the oil and some to the fuel and take her for a long ride on the freeway with a few full throttle blips. worth a shot before you spend $$$$$$