Highway 360 becomes Highway 31 (Pi'ilani Highway), which covers some wild-and-scenic coastline that is on the south side of Haleakala---the big volcano rises to 10,000 feet, this side marked by the Kaupo Gap and deeply fissured gulches and mini-canyons. Although you won't find sandy beaches, coastal access is frequent, at Nu'u Bay (petroglyphs, old landing with snorkeling) and other rock-pocked shores (including one with a sea arch).
This "backdoor" route is actually an easier and faster drive, but that is only "easier" relative to the demanding Hana Highway. The first four miles after Kipahulu can be hairy, with one-lane stretches and dirt sections. Never take this route during or right after heavy rains and watch out for rocks and debris in the roadway. After four miles the road becomes paved-potholed for about 8 miles past funky-iconic Kaupo Store and beautiful Huialoha and St. Joseph's churches. Highway 31 is then smooth asphalt, undulating with blue-water views all the way to Tedeschi Winery, and back around to the Hana Highway.
Maui Trailblazer has all the sightseeing details on this coast.