Wow, you just hit the way-back button for me. In the late 70's I had a 383-S Fastback (Green w/ Blk. buckets & 4 spd.) that I used to get about 6 MPG with. When Sunoco 260 hit the unbelievable price of 64 cents a gallon (for 106 octane, IIRC) I traded my Barracuda for a Cadillac and doubled my mileage to 11-12 MPG.
Sunoco 260.... wow. I also wonder what ever happened to that car....