Harmonic balancer help

I want a new harmonic balancer for my rebuilt engine. The local Napa store wants $122 for one. Does anyone know where to find one a bit cheaper? The ones for 81 and up are easy to find for $60 but the 79-80 are not so cheap.
 
Sorry, I guess I should have stated that mine is a 79 pace car. Jrichker, thanks for the info but i don't think I can use that one. I wonder what the difference is?

Early engines were 28 oz imbalance, later were 50 oz.

Try this - DAMPER KIT
M-6316-K351**
• New stock replacement damper for most 302/
351W engines with left-hand water pump inlet
• Fits 1970-1980 302, 1970-97 351W crankshafts
with external balance, 28.2 oz.-in. balance factor
• 4-bolt pulley pattern
• 3.950" overall length
• Includes E8TZ-B damper
and F1TZ-A timing pointer

http://www.mustangsunlimited.com/it...e&subCategory=Harmonic+Balancers&CatKey=74-01