Mine has almost 108K, 70k on this shortblock, and over 30K of that with a GT30 bolted to it. Most of my driving is highway, but she gets her share of flogging. Drag, Autocross, the "occasional street encounter", spirited merging... runs like a champ.
As long as you drive it, and there isn't anything noticeably wrong with it, I say go for it. If the guy has all the service records with the car, even better.