I found this site that did a test with the different style seals. http://www.wilesroad.com/tuneup3.html It got me thinking does it really matter? (looks like the PS-516 has been relabled to PS-3960)
Shaft Seals types.jpg
4 seal types.jpg
For example a Sta-Rite 17304-0100S cross references to a PS-200 (General Service Buna/Plastic $6 (BMFJF), PS-3960 (Buna/Carbon $13 (BCFJF), PS-3867 (Ozone Service/Salt (Viton/Carbon -$14 (VCFJF), PS-1901 (Commercial Viton/Silicon Carbide-$40(VLFLF)
The 1st letter is Secondary Seals (Buna/Viton), 2nd is Primary Rings (Molded Plastic/Carbon/Silicon Carbide), 3rd Metal Parts Stainless Steel, 4th Mating rings (J-Ceramic/L Silicon Carbide), 5th Springs All Stainless Steel.
Looks like the value is in the PS-3867 can be found for about $14 that is the Viton seal with Carbon rings.
Just looking at getting others opinions.