Re: Gas or ebike?
40mph is pushing it. Youy've got a bicycle, not a motorcycle. 25 to 30 is a reasonable speed to expect from a non-modified engine. Don't be fooled by some of the speed claims you'll see posted here. 40 is possible but not without some modifications and some clear understanding of the engine and drive trane.
There is battery technology available to allow a longer range but be prepaired to spend some $ for them. Check out our electric bike section for input on e-bikes.
Good luck, ride safe.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"