I am hoping to get by without premium. Probably will run 89 octane. Compression ration should be between 8.5 and 9 to 1 with 90 CC heads. Plan to use an MSD adjustable timing control so I can pull some out if needed. Really want to do a 440 so I can use the step piston design. Want to try to get some decent fuel mileage if at all possible. If there were more piston choices for the 413 it would be a no brainer.