The snout seal for the supercharger is made by several companies. The real good double lipped Viton seal is Chicago Rawhide #7968. It is about $25-$30, my auto parts stored ordered one for me.
You may want to ask for the better seal, #7968 , it costs a bit more than #7966 or #7969( the $5 seals ), but I've heard it holds up better and is closer to the Ford oem seal.
Less expensive seals can be ordered (Chicago Rawhide #7966 or #7969, about $5), from Glazier's Mustang Barn. Just call (1-800-523-6708) and ask for the Thunderbird SC seal.
TCM also makes seals for the snout.
TCM Part # Shaft Bore Width Style Mat.
20X47X7VSF 20mm 47mm 7mm SF VCS
20X47X7VTF 20mm 47mm 7mm TF VCS
Their website is:
http://www.tcmseals.com/
Bill E. at Super Coupe Performance may also stock some of the seals., you could give him a call.
My installation "tool" is a 4" length of 1" pipe with a cap on one end and a 1" to 1 1/2" adapter on the other end. Drives it in straight and true. Be sure and lubricate the lips of the seal and watch for it hanging up on the sharp edges of the machined step on the shaft.