Navy, Check under the fitting for an O-ring recess in the rack, it may be designed for an O-ring as noted above. While I normally just read here, I was compelled to reply because i just saw these in a Speedway Motors catalog. I've been trying to round up all the fittings for a similar job. Like this:
Power Steering Fitting, -6 AN to 14mm-1.5 O-Ring
They make them in different thread sizes.