Hi Pressure is a 5/8-18 or 18mm inverted flare fitting
Russell # 640380
Low pressure is a 11/16-18 or 16mm inverted flare fitting
Russell # 648050
The factory fitting up to 1976 was a 5/8 and 11/16 Bump tube O ring fitting
this is the fittings that the LEE box comes with you may want to confirm with the MFG
the russell # are the fittings you ned to convert to -6 JIC male fittings