Summits in 90 Minutes? In that neighborhood, you're looking for the mouse that roared! How about Pine Mountain, off of the Pinkham "B" road (Dolly Copp area)? It caps the northern Pressies to the north, and might fit your time constraints.
"Stock Farm" Mountain? Mount Hastings? Caribou Mountain? Don't know how fast your pace is, but these are all on or near Route 2 on the Wild River block.
Good luck, and let us know what you can loop in the time allotted!