SP1000 = Round Cylinders, no Luggage. Silver/Blue or Red/White.
SP II = 1987 only for U.S., factory-fitted Luggage (but somewhat light-duty), 16-inch front wheel, Brownish-Grayish-Green in color. I've owned two: my previous 16-inch front-wheeler and my current, 18-inch front wheel converted. They're both just fine. Don't believe what you read. But...I wouldn't be without one, which is why I'm on my second.
SP 3 is a different animal.
Only thing I'd think about: riding in modern traffic...two-up...the braking could be better. And oh by the way, two-up riding works for two average Europeans. But for two average Americans things can get a little cramped. And the rear pegs on the SP II are severely compromised when the bags are installed. the passenger can barely get his/her feet on them. You're lucky if you can barely get a heel on.
P.S. -- and if you're American tall (I'm 6'4") the windscreen is way to low on either one, and the turbulence will beat you brains out. Thus...a supplementary lip/airfoil is required.
P.S.S. -- I currently know of a nice Red/White SP 1000 for sale. Not mine...call Jim Hamlin at Hamlin Cycles in Bethel, Connecticut. It was sitting in his shop.