I always wanted (but did not get) an Ariel square four or a Honda four. Loved the way they sounded. I saw a bike with a Chevy v8 on it in California!! I think they are made in Fresno.
The V8 bikes are called Boss Hoss. They also have made, though I don't know if they still do, a V6 version...which they kinda dubbed as a "ladies" bike. They're powerful, heavy, and expensive!
Ahh! But the power! You would'a loved my 70 Ossa Pioneer 250. Thirty three horsepower stock and bored three over. That thing ate every dirt bike alive at the time. Back in '73 we'd blow Harleys away with little Yamaha RD 350 two strokes.
Here's a 1970 Kawasaki Mach III 2 stroke and Yamaha RD 350. Mach IIIs were scary. Poor frame design, they had a nasty habit of doing wheel stands at the slightest throttle. One time a customer test drove one in the parking lot of the dealership I worked at. He cranked the throttle and that sucker stood right up, his feet came off the pegs and he smacked into a brand new unsold Merc. Pushed it a foot sideways..didn't do the bike any good either.