I'm betting the
Thule 554XT Hang-Two surfboard rack is exactly, if not darn close to, what you're looking for. This rack for surfboards mounts directly to your 1998 Ford Expedition roof rack crossbars, so there's no need to spend big on a multi-purpose base rack system that replaces the Ford Expedition factory rack. Each Thule 554XT Hang-Two carries up to 2 surfboards. If you need to carry another couple of surfboards then you can attach another 554XT surfboard carrier along side the first 554XT system on your factory rack crossbars. Like most SUV's and larger vehicle models the Ford Expedition has a wider rooftop than smaller cars. The wider cartop means your cross bars are longer providing enough room for two of these surfboard carriers to attach side by side.