Do you mean the 4114036 housing with studs? I'm having difficulty spotting 0411407 in that pdf document; are you sure your number wasn't a typo?
The upper and lower AC/heater boxes would almost certainly be salvage yard parts.
The good news is those housings would have remained identical for quite a lot longer in the production run than just up to 1981; they likely remained unchanged all the way up to about 1994, when the body underwent its next major redesign.
I'd suggest checking sites like parts voice, having a salvage yard do a nationwide part search, or keeping an eye out here for anyone parting out a van, which happens pretty frequently. You'd almost certainly get better pricing from another Vanner or a pick 'n pull salvage yard.
-It's been such a LONG TIME... BlueShift>>
1981 Dodge Ram B250 Custom Sportsman Maxi Van
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