TR3 Thin Fan Belt and Pulleys

Seasons Greetings listers,

I plan to convert my TR3 to a alternator this winter.  The thought of 
going to a thin belt interests me.  What's the pros and cons? Looking 
through the main catalogs I fail to find a "kit" of pulleys and such 
for the changeover. Surely, someone offers something.

Bill Quincy
Wichita Kansas