Custer through Hill City to Rapid City then back to the Thunderdome via US-16 to I-90:
(73.0 miles, 1hr 25min). Quickest Route with some Scenic views.
Custer back through Deadwood to the Thunderdome via US-385 to US-14:
(72.5 miles, 1hr 38min). More of a straight shot with Lots of Scenic views.
Custer back to the Thunderdome via Needles highway and Iron Mountain Rd to Keystone to US-385 then back through Vanocker Canyon Rd:
(95.2 miles, 2hr 54min). Very Scenic with lots of Winding Roads and Hills.