this unit probably has a Roush conversion (NASCARs Roush Racing) these conversions are sanctioned by Ford and are usually done by Ford dealers when the vehicle is new. this system differs from the older systems that it injects the liquid propane into the intake manifold
where the older systems used a special carb. that vaporized the propane as it enters the intake manifold, that was the reason they were so hard to start in cold weather. this conversion is more popular with fleets in urban areas that have their own propane source on site