R3 Header question

[Avanti1963!]

I have what I think is a pair of unused R3 headers.  Three pictures are attached.  Please help to answer a few questions. 

-The left and right look exactly the same. 

-These don't have the alternator bracket sticking out of the front of the passenger side. 

-There is a part number 1558353 cast on the right horizontal face on each.   On the other front face is cast 206-86. 

-Pictures of the reproductions don't seem to have a number.

What do I have?  What models do these fit?  

Thanks

Edited 16 hours ago by Avanti1963!

[mfg]

Not sure, but I’d guess you own the real McCoy… Amazing how, after all these years, rare parts like these still turn up !

[Nelson]

They appear to have been port matched. They certainly look original issue but I think the Lionel Stone versions were cast from the same tooling so I think those had the numbers also.

[Dwight FitzSimons]

Left & right exhaust manifolds ARE identical on ALL Studebaker Avantis, whether standard R1-R2 manifolds or R3-R4 "headers."  There was no need for a boss for an alternator bracket on Avanti manifolds.

Your R3-R4 manifolds will fit any Studebaker V8 from 1955 through 1964, whether 224, 259, 289, R1, R2, R3, or R4.

I have a set of Studebaker International's reproduction R3 headers and they have no numbers or letters cast into them, so yours are not the most recent repros. 

--Dwight