71-73 Mustangs were never built with a 351W. If your Marti says it was, then the report has a typo.
As Stanglover noted, that's a factory 71-73 Saginaw steering box, not a Borgeson unit. The first pic of the box where it's greasy and dirty, it shows an ID tag in place, what's the code stamped into that? It should be SPA-xx
The inlet is 11/16 female inverted flare
The outlet is 5/8 female inverted flare
My recommendation is to purchase the 71 pressure and return hoses. Use those to determine your routing and mark the pressure hose where it will meet the modern pump. Bring the pump and the hose to a hydraulic shop and have them crimp a matching fitting onto the 71 hose. Around here, many NAPA stores make hydraulic hoses. The 71 return hose is cut to fit and will most likely slip right over the return nipple on the pump reservoir.
https://www.rockauto.com/en/catalog...92,steering,power+steering+pressure+hose,7320
https://www.rockauto.com/en/catalog...2692,steering,power+steering+return+hose,7324
F1SE casting number is a 1991 and later 302 / 5.0 block. IIRC, they were used through the end of production in 2001, and likely thereafter for service supply.