Need help with gearbox!

[Tim Tichgelaar]

I have an engine that needs right side chain drive to fit in my frame, but of course that means my bike would go backwards, so i need a reverse direction gearbox with 1-1 ratio, ive found a few with 5-1 but my gearing is already good

 

[5-7HEAVEN]

What's your gearing now?

Were you going to chain the engine to the
rear 8-speed cassette?