Started getting the parts together for my router. Purchased some 608-2RS ABEC7 bearings but when they were matched up to an 8mm bolt the amount of slop was tremendous. Is there another alternative or does everyone just apply tension until the backlash is out and let the axle wear against one side of the inner race?

When you tighten the bearing onto the bolt, the slop will go away. You can use a 5/16 bolt as well, because it's about the same size as an 8mm bolt, neither being actually 8mm, and the 5/16 are usually cheaper.