Glad to see your Mossberg 500 starting to come together now. I really like the marinecote finish on yours. I assume you didn't have any issues installing the heatshield and other items.
The picatinny rail screwed right in with ease into the existing holes that were pre- drilled and tapped.
As far as the rail under the heat shield; that was fairly easy as well to install.... now I just need a red dot scope for it.... but I just can't decide!