Keith Craft put a Professional Products one on my 482.
He's got them on his website. They're a 7.5 FE Zero balance dampner. Part # 90009 It's the:
Ford Powerforce+Plus SFI Harmonic Dampers
http://keithcraft.com/vp500/shopdisp...ional+Products
PP also has them and here's a link to their website.
http://www.professional-products.com...ductBBford.php
Dan