1998-99 I would say as H-D always makes inprovements to there motors, by reason of the last years they where made. The evo is such a good motor everybody copies it. Of course S&S / Dacron and others make stronger cases but its still the evo basic design.
If your talking about a totally stock motor than it would have to be from 97 on. This was the year the lifter design was changed to the better style, also I believe this is when the base gaskets were changed to a better type but they still leaked. The later EVO's (early 90's) had an accelerater pump on the CV carb as compared to the early 80's with no pump. They also had a better ignition on the later ones, (better advance curves).
H-D TC88 Touring class bike, prefer 2002 because of the chassis improvements. Also there have been some upgrades to motor components but you'll have to ask a real wrench about that. Also the 2002 models have new EFI that is compatible with the HD Race Tuner.
If I was buying, my current choices would be:
#1 Road Glide
#2 Electra Glide Classic
#3 Road King standard
I'm 32 years old. I like to ride fast and long, therefore I like a fairing. I like having a radio. I wish I had cruise control on my '98 FLHTC. I like my bike with as little excess stuff on it as possible (easier to clean, and less weight=faster)
it really depends on what youa re going to do with the motor.
Stock evo to a stock TC88, the TC88 is better all around. But if you were going to build a monster motor I would go with a evo (ss113 or Merch131). If I was just going to buy a used HD a TC88 would be first choice if money was no object, but you can get some older evo bikes for a damn good price. I would even buy an old shovel, but most people ask too much for them IMHO. It all just depends on what you got($) and what you want.
Another good thing about evos and shovels are that any shop can work on them, or just about anyone w/tools,time and a book can too. But a TC88 you may end up with a dealer only type problem. Plus most of the problems with them are known and solutions already discovered. As with anything new the TC is not that way.