I think you're primarily asking about availability of lower LATCH anchors, the pairs of small metal bars in the vehicle seat crease which can be used instead of the vehicle seatbelt to install a carseat? Due to their sizable gross vehicle weight above the federal cutoff for requiring factory equipped LATCH, Ford F350 models are exempt from the LATCH standard and are not factory equipped with lower LATCH anchors (the "LA" in the LATCH acronym which stands for "Lower Anchors and Tethers for CHildren"). There is no retrofit available from Ford nor aftermarket for lower LATCH anchors for the F350, either, so you're using the only proper installation method possible in your F350, the vehicle seatbelt. As long as your carseats can be installed with the vehicle seatbelt independently of each with less than 1 inch of movement at the carseat's belt path, then you have proper installations.
Despite being LATCH exempt, though, Ford typically does voluntarily include factory equipped top tether anchors (the "T" in the LATCH acronym) in their otherwise LATCH exempt vehicle models, depending on the model year, so it's possible your F350 Super Cab is factory equipped with top tether anchors. It may be possible to retrofit top tether anchors if it isn't factory equipped since Ford also has a top tether anchor retrofit program for eligible pre-factory equipped Ford models (not lower LATCH anchors, it's a top tether retrofit program only, Ford Program R7C
http://www.car-seat.org/attachment.php?attachmentid=19326&d=1357607813 through Ford dealerships). You can and ideally should use the top tether anchor for a forward facing harnessed carseat installation (you can use the top tether with a seatbelt installation of a forward facing harnessed carseat, or with a lower LATCH anchor installation of a forward facing harnessed carseat if the vehicle is lower LATCH anchor equipped) if the vehicle seating position is appropriately equipped with a top tether anchor. Top tethering serves to reduce head excursion, the amount the child's head moves forward/beyond the carseat's protective shell during a crash.
If you post back with your F350's model year, someone here with a LATCH manual can likely look up its specific details to determine if your F350 already has factory equipped top tether anchors, or if top tether anchors can be retrofitted through Ford's program if it's not factory equipped with top tether anchors.
