I just picked up 3 bottles of Castrol SRF from Amazon.com, the "sub store" that sold it is called Powersport Superstore and it costs $67 plus shipping.
Track / Autocross setup: Forgestar F14 (21.8lbs & 23lbs)
Front: 275/35/18 Continental slick on 18x10, Rear: 305/35/18 RA-1 on 18x11
Drift Setup: Front: 275 Continental slicks, Rear: 255 Michelin PS2 street tire
Laguna Seca previous record - 1:49:498