For a rental set that contains a complete assortment of shims, try SHO NUT or other SHO specific source. To purchase new shims see the list below.
Valve shims: Motorcraft E9DZ-6515-xx, where xx = N to EA
Thicknesses 2.300 to 2.675
FordPartsOnline.com $3.04 each
FordPartsNetwork.com $3.15 each
SHO NUT Performance $3.55 each
Thicknesses 2.700 and up
Yamaha 2.700 K&L 13-7649, Yamaha dealer $19.95 (5 pak)
Yamaha 2.750 K&L 13-7650, Yamaha dealer $19.95 (5 pak)