Yeah they're billed as a summer marathon tyre for various terrains. Quite narrow for a 2.1 so might cut through the gloop too. Very light as well. Haven't tried them yet though.
Just received some NOS Chris King parts for the no logo headset but $$$ :roll:. Mailed Chris King direct and they managed to find some parts for the old type headset, pretty cool but maybe OTT for this build.