Those Williams-Bachman sets for the F3 and F7 are still out there NIB on some sites, but for some reason the F7s are priced as much as $75 to $100 higher than the F3s. I would prefer to get an F7 set, because I like shorter engines, but have to ask myself if that justifies paying so much more. (Especially since I would be getting rid of the dummy unit.)
Mannyrock