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Reckon you can get away with your existing road tyres on the 130km ride, from your calculation, you got about 90km of road riding, I did ride the standard G-One 40mm on the road and was pleasantly surprise at how easier it is to roll on the tarmac.
Given the location and date of Dirty Reiver, it's not gonna be 100% dry, maybe go for the standard G-One, personally would go for the G-One Bite for better traction off road than on road if given the choice.
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If you like, I do have a pair of WTB Riddlers (tanwall, wired) in 700c 37mm I can sell to you for £25? it came with my Arkose and never even been ridden as I swapped the wheels for 650b.
http://www.roadbikereview.com/reviews/wtb-riddler-tubeless-gravel-tire-review
Speed appear much more focussed for road riding (feel slick), with the accidental towpath, whether Bite is the exact opposite.