I wouldn't use any of the legs in the Vika lineup for a something of this size, nor for such a heavy top - they aren't designed for that.
The Galant legs are a lot sturdier, and they do have ones with casters too ...
IKEA | Drawer units | GALANT system | GALANT
... except they aren't height adjustable. You will need an underframe for this, though, so that would add a like an 1 or so in height at the ends.
Still, I think it's extremely pushing it to have an 8-ft. span without any additional support mid-way - the top will sag. Besides, these tops are HEAVY; it'll be like moving a stove in and out all the time.
(I should know how heavy they are ... I pulled a muscle in my hand helping to lift one of these countertops,)