Dennis, I have successfully used thickly-cut leftover smoked meatloaf slices, cut into cubes, as meatballs.
For what it's worth, I'd rather make smoked meatloaf once and use the leftover slices (broiled, to add a slight crust) as another entree or for sandwiches, and use more of the leftovers (if any) for meatballs.
George is right. Add some BBQ sauce to your meatball sauce (add a little BBQ sauce and then taste to see if the proportion suits you). Good Eats!
Rita