I'd probably look for a Trek 520 Touring frame. Maybe something like a road triple with 28/38/52 chainrings, whatever gearing for the back, Shimano brifters for the brake levers and shifting. Maybe Old Man Mountain racks front and rear, Ortlieb panniers. Some nice 36 spoke wheels laced up to Phil Wood hubs. Some shallow drop alloy bars. It's not really about the bike, more about the trip.