Very nice find! I used to run on a 4 lane Artin set like that and I think you got a steal of a deal.
The slot between won't be much of a problem for cars with wider tires. If you run old F1 cars with narrow tires, it might get a bit challenging but those don't normally swing wide in the corners either :lol:
Evergreen plastics also makes a U-shaped extrusion that bridges that gap perfectly. I used hot glue to hold it in on the straights and shoe-goo or rubber cement to hold it in on the corners. A touch of paint hides it and you have a great, smooth track.