I have not had any problems with child seats in my '99 F-250 Super Duty, Super Cab.
Almost 2 years ago, when I first got my Super Duty, my youngest one was only a couple of months old. I had no problem putting a rear facing infant seat in the back, BUT, my truck has captains chairs so there is no front seat back in front of the center position of the rear seat to interfere.
Currently have:'99 F-250 Super Duty, 4x4, SC, XLT, 5.4L, 4.10LS, Deep Metallic Blue/Med. Graphite, Superchip.
On order: '00 F-250 Super Duty, 4x4, SC, XLT, 6.8L, 3.73LS, Island Blue/Silver with Med. Graphite Interior, Ordered 10/11/99, Still "Clean and Unscheduled as of 2/1/00, So I cancelled the order.
NOW on order: '00 F-150, 4X4, SC, XLT, 5.4L, 3.55LS, Off-Road, Island Blue/Silver with Dark Graphite Interior, Ordered 1/20/00, Serialized 1/27/00, Build Week 2/14/00, Shipped 2/18/00.