Well, remembering how homes were built in the early 70’s, this dosen’t surprise me at all.
This looks as strong as the part of a bridge it was holding up at one time, and another improvised frugal owner that got it from someones back yard.
In my area, back in the 70’s, homeowners that wanted basements under their garages would use 90 # rails from railroad tracks to span the width of their garages and hold up the concrete slabs.
They were also reinforced with potatoe digger lags for reiforcement that they got for free from a farmer.
Code, hell, what was that, geeze, I just started learning FHA Code requirements in 1970.
The ones that had a book of Architectural Standards was lucky like me. Copyright 1968. Still have it.
If it was proven to be strong enough by previous use, it was good enough.
Long way from meeting todays standard, but that is the way it was.
If it has been there that long, I am sure it will be there longer than the wood framing that it is supporting.
Note what you see and move on, is the best thing to do.
As far as being adequate, well let us just say, it worked for this long.