71 Duster ? power steering box ID

Hello all, it's been a while! When we put together the 71 Duster for my ex-wife, we swapped the manual steering for a power setup from another A body.. A friend orchestrated the trade, so I don't know exactly what year & model the PS setup came out of. Life happens; the car now has a new owner, a friend from a couple of states away. the power steering box now needs replacing, & his shop is reluctant to order the part until he knows exactly what it is. Is there a way to identify these boxes (casting numbers, or any other visual identifiers that might tell him the year, etc.)? I think the shop doesn't want to waste their time chasing the part. Any wisdom I could pass on to my friend would be greatly appreciated!