My understanding is that the "Flaming River" box is cast iron unlike the Mopar units that are a light cast aluminium.
My steering box is actually a "Firm Feel" unit. These are rebuilt from original MoPar boxes.
Stock power steering has a ratio of 16:1 (3.5 turns lock to lock)
The stock manual steering ratio is 24:1 (5.5 turns lock to lock) so as to make the steering lighter.
However MoPar did make some 16:1 ratio manual boxes for racing. But these are rare and hard to find.
Firm Feel take stock manual boxes and convert them to 16:1 as well as a half way 20:1 ratio (4.5 turns). The latter is the one I use.
I supplied a core for them in order to keep the price down. Their own cores cost $200 but you can find them for half that or less. Much less if you are lucky.
Firm Feel are at
http://www.firmfeel.com/manualst.htm