3rd year in a row I'm running the half-marathon. I park on College Ave and take the shuttle to the starting line on Busch. You finish the half marathon on College Ave right by Scott Hall, so your car is there when you finish, not sure of the 8K route.
Park in the surface lot by the frats where the grease trucks used to be if you want to be near your car at the finish, again only if the 8K finishes on College Ave..
Usually arrive around 6:45 AM, half marathon starts at 8 and the 8K starts at 8:15.