Simple, actually.
Horizontal Kinetic Energy = [.5]m*v^2, with m being mass and v being velocity [simplified to the scalar 'speed']
Mass can be neglected, as it's constant.
So... 13mph = 5.8m/s.
KE at top of lift = 16.82 units
KE values can be added, so we add in the drop factor, which -- neglecting friction, etc -- is mgy. [Mass, Gravity {9.8m/s/s} and height in meters]
Drop KE = [neglecting mass] 9.8 * 91.44 = 896.1 units
Add the chain and you get 912.93 units. Back to horizontal gives 42.73m/s or 95.58mph max.
SD's is [assuming 5mph chain]
KE top = 2.5
KE drop = 9.8*94.488 = 925.98
Total = 928.48
This gives a max of 96.40mph
So both running at maximum speed, SD is about 0.8mph faster.