Sam, not sure how long the Streetsweepers were used but eventually they were joined by the Sound Off Signal RoadRunner, both were mounted to the coil cover.
RoadRunner on an '88:
Looks like a Street Sweeper on a '90:
I don't believe the Street Sweepers are still being made but the RoadRunner is still in the catalog.
RoadRunner with current markings:
RoadRunner with vintage markings:
The siren amp was mounted below the main radio board. I didn't have any extra holes in my trunk floor in that area to indicate another mounting board may have been used so we just mounted it upside down onto the bottom of the main board.