Akira, I found a nice one but the seller could only tell me it's a K-version which I already found out using Roland's database. So no idea if it's already AI-d.
I'll pass on this one.
I can only speak about Japan, but...
The K-version was current during the transition period from non-Ai to Ai. When Nikon released the earliest Ai bodies F2A, AS, Nikomat (domestic name for Nikkormat) FT3 and Nikon EL2, they offered the free conversion service of the existing non-Ai lenses to Ai (one lens per one newly purchased Ai body). Of course, Nikon offered Ai-conversion kits for many of the pre-existing lenses, and non-Ai lenses could be converted at Nikon for relatively low cost. As a result, there are plenty of non-Ai lenses officially Ai-converted, and their serial numbers are much younger than the ones indicated in Roland's website.
It is very easy to tell the factory Ai-converted K and non-converted K. If the light meter coupling prong on the aperture ring (rabbit ear) is perforated, and there are two aperture scales on both sides of the prong, it is factory Ai-modified K lens, assuming that its serial number falles within the range for the K version.