I would love to do this ride. Right now I am not sure if either of my bikes (Specialized Roubaix, Sirrus) would be ideal. I don't want to have a miserable time. I will try to explore some modifications or different tires that may help.
It used to be said that there was no "perfect" bike for this ride. With the rise of the "gravel grinder" segment I suppose that has changed. You see everything from hardtails to carbon bikes with 25's.
Tire clearance likely takes the Roubaix off the list. For the Sirrus, I would guess you have room for big tires, but the flat bar would make for a long day. A friend put drop bars (and barcons) on his Specialized hybrid (maybe it was a Sirrus) and had a blast. Cheapest option may be to get some ski-bend bar ends and call it good. Plenty of hand positions and no need to change the shifting.
Although perhaps this is an opportunity to go N+1
