Disributors actually recalled most of the 70 cc kits because of quality problems so a 60 cc kit is probably a better solution just now until the 70 cc kit problems are resolved.
Most people buy the kit with the Bi Turbo. I think your results may vary. I would expect you could get 37-45 with this kit. Make sure you brakes and tires are in good shape. You should also expect better hill climbing perfomance with the upgrade.