The personalized license plate indicated the engine size. Note the antique V-8 emblem above the plate. My engine was a souped up V-8 Corvette engine (Chevy 350 short block). I think they used that same engine in your 1960 era Iso sports cars. The Boss Hoss bike alone weighed over 1,200 pounds (550 kg). It weighed about 1,700 lbs with the sidecar and was 8 feet wide! It took up the whole lane of most wide American streets. You had to pay extreme attention operating it at all times. There was no room to make lane corrections ( I call this "Jesus factor"). It scared the hell out of most Harley riders. It had no "Jesus factor", you drove it very carefully, or you crashed! You could not even hear a Harley 1,450 cc engine next to this bike. It was very loud. Everyone could not believe what they were seeing when I drove it.  This bike was very frightening to drive. The new owner was so frightened, he removed the leading link front end and replace it with a Harley Servi-car front end and triple tree. It handles much better now. The Boss Hoss was an interesting project to complete, but I never would want another. It is too much bike, too much engine, too heavy and your knees get very warm whole riding near the manifolds. Boss Hoss bikes are very popular in the Southern United States and many guys even put Chevy 502 engines in them now with Nitro. We are talking zero to 60mph in less than 3.5 seconds. Zero to 100mph in less than 6 seconds! They are crazy!!!

Let's start with something really different!!!
Many thanks to Todd for words and pictures

LAVERDA 750 SFC & DUCATI MHR MILLE TT1 owned by Seiichi-Horie (Japan)