Hi, my 67 gtx clone has a leak at the return line at the pump. Pulled the hose off today and some has a 5/8 heater hose over a 3/8 fuel line at the pump. At the box the fitting is 5/8, the fitting looks to be alloy, two bolts holding it to the control valve. My question is what is should it be at the box, if this is correct it must use a specify return hose with 5/8 on one end and 3/8 on the other. thanks

My 67 GTX has the same deal, and so does my 67 Coronet. I have posted on here about it before, but no good response. The outlet nipple for the return hose on the pump is 5/8, but the steering box valve is 3/8. I wound up using brass fittings to reduce it. I saw a magazine photo of a 66 Sattelite with a plastic reducer fitting with the correct hog-ring style clamps. There must have been some kind of reducer, but you are the only other person I have seen post about it. I need one too !

I did get a plastic 5/8 to 3/8 adapter, so I have about 2" of a oil resistant rubber hose and then about 8" of 3/8 power steering hose. Hope to learn what they used at the factory. thanks old school for the reply. dale

You have the same problem at opposite ends if I'm understanding right....My 66 box had the large return fitting, now manual, my GTX box has the small.....
When the federal style pump went on my GTX I changed over to a saginaw style and the return hose is the small size so no problem..The pump I replaced had the small size also so maybe in the past 40 plus years the pumps have been swapped? You might be able to just unbolt the fitting from an old swap meet junk box and swap them or change pumps....I looked in my 67 factory manual and don't see any factory adapter type fitting.
My 66 had the same size return fitting pump and box and the 67 did also...