The Randal 160mm Downhill Trucks are great for high speed (40+MPH) downhill longboarding. These trucks will work on drop-through and top-mount boards. If you want a tuck that carves good take a look at the Randal 150mm or 180mm.
Please note that Randal 160mm DH Trucks have the old school hole pattern (the bigger one). If you longboard has the new school hole pattern you will have to drill your own holes.