63A gearboxes for an L Series engine are NOT UNCOMMON in Australia, but 63A gearboxes for an A Series are NOT AT ALL COMMON in Australia. If you have an A Series box, you need an L Series front casing and the L Series input shaft. If you can't get the L Series parts in the US, I'm sure someone in Ausrtalia will swap you the parts for your A Series front casing and input shaft. I do recollect that some models of the later series 510 sedan might have been fitted with a 63A box in the US. I'm sure someone will know. The 63A (dogleg) transmission was fitted to both 180B coupes and also Stanza SSS models in Australia, both with L Series engines and they are (reasonably) available here. I don't know of any Datsun model sold in Australia that had an A Series engine and a 63A gearbox.