I know Saginaw went to metric fittings in 1980, but how far forward can I go to scrounge the metric fitting to retrofit my old pump.

No need really, you can use the stock SAE flare seat hoses from your old pump to what I presume is your new steering box with the metric o-ring seats by calling up Lee Manufacturing and ordering the adaptors, they run about $15.00 shipped to your door. Their number is 818-768-0371, once their installed, no one will know the difference, trust me, you can't even tell.

Yes, or I could change over to -6 AN hoses with a couple off the shelf fittings but from what I understand I'd still need the 1400 psi valve anyway.