I did Wabeno to Munising last Feb. From Trump Lake to the Buckhorn was 210 miles.
Route was -- NST to Trail 2. Trail 2 east to Trail 116 north then Trail 16 east to Crystal Falls (Gas Stop).
Continued Trail 16 through Sagola then Trail 5 to 32 north to Gwinn (Gas Stop). Trail 8 the rest of the way. Buckhorn is on Trail 7 south.
This link is helpful too. Too bad it only covers a small area, but enough to help.
https://trailgenius.com/trail-genius-map/snowmobile-trails-marquette-county-mi
Another note 1 - If trail from Crystal Falls to Sagola is not groomed yet, I would take a different route. It was groomed for the 1st time just one week before our trip last year.
Note 2 - We rode this route on a Monday. However the high line trail (straight shot) for about 25 miles east of Gwinn was 2-3 foot moguls. That was the only bad section of trail that we hit. It was so rough that the group in front of lost all of their oil that was strapped to the back of one of the sleds. There was oil everywhere. The jugs just exploded.
We also hired a guide who took us out to and around Grande Island.