Lars, 5 weeks to make the pistons was what I was told, too. I think we are in the middle of week 5 now. I'll shoot them an e-mail tomorrow.
About camshaft -
I think I'll give it a try to put SR43A camshaft in SR42B. I am quite sure there will be no mechanical conflict.
Like Wundis already pointed - I am curious too how the camshaft will act with different CDI (read: ignition timing) it was not designed to work with. I suppose it shouldn't be a problem, since many aftermarket cams are produced for BIGs and they don't care if it goes into SR41 or SR43, A or B model AFAIK.
And then there is another possible mod called tunable CD Ignition which allows you to design your own ignition curve in your computer
I hope these guys are still in business: http://www.ignitech.cz/english/aindex.htm
Look for section "SPARKER DC-CDI - capacitive ignition for 1 cyl. motorbikes" on their site.
I am not too serious about this mod right now but the idea has haunted me since I read SR43 had different ignition curve.
OK, over and out now. I think I am just overthinking and should get working on the bike finally. Snow is already melting here...