Paul, Have you seen this diode: RHRG75120 1200V at 75A TO247 case with 2 legs.. Would it be a good subtitute for the STTH6002CW?
Data sheet:
http://www.fairchildsemi.com/ds/RH/RHRG75120.pdf
There is a guy selling these on ebay, 4 for $10.60 Free ship
Ultra Fast Recovery Power Rectifier 1200V 75A 85ns (x4 - eBay (item 220425461517 end time Jun-30-09 09:56:38 PDT)