My 55 Thunderbird 292 has a Casco Alternator conversion.  I have been chasing an intermittent fan belt squeak for some time.   I installed a new water pump thinking I may have had a bad water pump bearing.  The new water pump turns freely.  The belt groves are aligned correctly. I installed a new single fan belt from my local auto parts store.  The Alternator charges great and turns freely.  I tightened the alternator as much as possible, but the squeak remains.  I have an electric fan only.  The squeak begins on startup when the engine is cold.  If I hold the RPM around 1,500, the squeak is constant until it runs for a few minutes. When this happens, the alternator pulley get very hot. I assume the belt is slipping in the alternator pulley?  The Casco alternator pulley grove is not as deep as the stock Ford water pump and crank pulleys.  Is there a special Thunderbird fan belt?  Anyone run into this before?  Thanks!