iirc the oldschool ninjas (like what you've got) made ~45 horsepower out of the factory, and this site says the same:
http://www.motorcyclespecs.co.za/mod...ninja_250r.htm
Consider age and all that junk. I'm also not sure if that was at the wheel or the crank. Site also lists 17.7 lb-ft
I don't think an automatic transmission is feasible, but what this guy did with a CBR engine and a Tuk Tuk doesn't look like a bad setup:
Link to original page on YouTube.
Also, if you search around I do recall a member sticking a garret turbo on his bike, but I'm not so sure he ever got it stable.
Welcome!