If you own a Lycoming powered aircraft it's probably best to check out their latest announcement concerning the "retirement" of certain crankshafts.
http://www.lycoming.textron.com/main...569/index.html
MODELS AFFECTED: Any Lycoming engine model specified below manufactured, rebuilt,
overhauled, or repaired after March 1, 1997:
Lycoming counterweighted (L)O-360, (L)IO-360, HIO-360 and AEIO-
360 engines described in Section 1.
Lycoming IO-390 and AEIO-390 engines described in Section 2.
Lycoming O-540, IO-540, AEIO-540 and (L)TIO-540 engines described
in Section 3.
Lycoming IO-580 and AEIO-580 engines described in Section 4.
Lycoming IO-720 engines described in Section 5.
Lycoming crankshafts with a crankshaft serial number listed in Table 5
shipped as a spare after March 1, 1997. These crankshafts may have been
installed in any of the engine models listed above.