I started using a 4 hole spacer after I read this tech article
http://garage.grumpysperformance.com...fication.1038/ and later started this thread
http://67-72chevytrucks.com/vboard/s...d.php?t=747364 I've since swapped the one in the thread for the Summit plastic one and find it to be better phenolically (hey, is that even a word?).