FW has converted two sites to pull through the last time I looked.
You can request a pull through during the reservation process (it's in the comments), but as with all requests nothing is guaranteed.
As always, I recomend making a reservation and making reasonalbe requests based on the camping rig or the needs of someone staying at the site.
Length of rig, number of slides, number/size of awnings, screen rooms, needs to be close to a comfort station should all be noted. After that it is up to the site assigner to match your needs to the available sites.
Remember, the site is not assigned to you until the day before your arrival. It is at that point that the assigner matches needs to sites available.