Hello, can anyone please help me. I have a Suzuki samurai 1.9td, bought in Portugal. It needs a new primary shaft in the (manual) gearbox. Will this part from a Suzuki Santana, bought in England, fit or is the shaft a different size? Thank you for any advice on this problem.

Do you mean the shaft between the transmission and the transfer case?

Do you have a replacement shaft? If it went out, the gears may be damaged.  You need a press to rebuild it. It way be cheaper to replace it

The gearbox components on just about any SJ413-series Suzuki are interchangable.

There were a few internal changes in the US-version (5th gear ratio, electrical connectors, shifter lever/tower construction) but I do not know if the changes also applied to other countries.

Your BEST choice would be to find a complete transmission from the same year as your Suzuki SJ-413/Samurai/Santana and swap the whole gearbox/transmission.  It is difficult to tell which version is which unless you know exacty what you are looking at.  You should be able to find one at a salvage/breakers yard.

I hope that this helps!