This should help:
http://www.jalopyjournal.com/forum/s...d.php?t=303600 scroll down to #5.The pass side outlet water pump was last used in 1969 as was the 3 bolt harmonic balancer,70 and later pumps were longer and on the drivers side,READ carefully the article I wrote,if you use the 50 oz balancer I suggest you can use the short water pump you have now as this balancer has both 3 &4 holes for pulleys.Here is the correct pulley set for the short pump and balancer:
http://cgi.ebay.com/ebaymotors/Small...Q5fAccessories