These are my observations so view them as being informative and not facts:
1) Concerning the Chevrolet 250 engines and South America, countries north and west of Brazil tended to offer 250 engines similar to those in the USA.
2) Brazil and Argentina were more independent concerning Chevrolet 250 engine development. OEM two barrel manifolds were commonly installed.
Over the years I have acquired: 1)Argentine two barrel intake manifold 2) Brazilian two barrel intake manifold (alcohol version) 3) Brazilian two piece cast iron exhaust
The acquisition process have not been consistent. I have ordered all while in the USA. Some attempts have been smooth and quick, some have fallen through, some parts have been slightly different than pictured and stated (alcohol versus gas intake manifold), some have taken months. Some shipments have arrived in a week, some have taken 4 weeks.
You can search using the following sites:
Google Brazil, Google Argentina, Google Peru
Mercado Livre Brazil, Mercado Libre Argentina, Mercado Livre Peru
Some foreign words to use searching:
Intake manifold: admissao coletor (Brazil) or colector (Argentina)
Cylinder: cilindros
6 Cylinder abbreviation: 6 CC
Engine: Motores
Brazilian Cars using the Chevrolet 250: Opala, Caravan
Argentine Cars using the Chevrolet 250: Chevrolet 400, Opala
There is an Argentina road racing series that uses 6 cylinder engines, the Turismo 4000 Argentino
http://www.youtube.com/watch?v=1bo62j9S1TUThis Argentine site has a Chevrolet 250 OEM style aluminum cylinder head:
http://www.crparts.com.ar/verart.php?id=542