'87s are prone to electrical problems. '88s were redesigned to eliminate the problems.
Up to 2000 had manual cam chain adjusters, drum front brakes, and kick starters.
2001 and later have a more powerfull charging system to power a brighter headlight, front disc brake, automatic chain adjuster, and no kick starter. There is also a different carb, but no real difference in functionality.
The ideal TW would have the 2001 and up electrics, cam adjuster, and disc brake and the 2000 and older kick start mechanism.