I did this route many years ago (1980s) on public transportation…is this still possible, stopping overnight in Lishan? I think the point of departure was Taichung.
Highway 8 has been closed for years between Guguan and Lishan and will not re-open anytime soon. You can only do the trip on Highway 14, via Puli, Qingjing, Hehuanshan, Dayuling (there you can make a left if you want to visit Lishan), then down to Taroko. Or you do the Yilan-Lishan-Taroko Route.