Bike really depends upon the terrain. I did 3 50-60 mole races on my 96 hei hei in 2014 and that was so brutal. Swapped in 60 mm fork and vbrake in front but my hands were bruised blue at the end.
Problem was 6000+ elevation gain meant the same rowdy descending and cantis need serious strength so gripping bars hard while absorbing hits.
I rode 2.25 aspens which are supple, rolled fast and fit in the frame. Great tire. Unfortunately the 26” really doesnt roll well over roots.
My advice is roll the biggest tires you can setup tubeless. Moderate tread or the rolling resistance will murder you.
From the hei hei i moved to more modern bikes with disc brakes, a 120/100 fs bike, then a 120/135 fs, finally to a 29er ht.
The two biggest differences was disc brakes and tubeless, the tubeless rolls fast and rides smooth. I rank them both higher than a front fork.
Other than the complements I have no fond memories of those races on the hei hei, my hands still hurt when i think about it.