502 IV 671 Blower Install

Looking for anyone else who may have installed a blower on thier 502. Mine is a gen4 motor. Stock with about 3k miles on it. My darling bride bought me a 671 blower for christmas (I guess this prooves just how much she loves me). I'm told by locals that I must O ring the block. Ant other tips from someone who's already been there would be great. The car is already bad as hell. Now it will really be the sh**t