77mm pistons accralite or wossner direct i think is your best bet to be honest although not sure on stock levels dont think they sell in huge number so shelf stocks may be low expect a 2 week wait.
best place for quality shells is vw although they come with a hefty price tag, a good quality supposed oe spec manufacturer of shells is ks or kolben schmidt i think is there full name i got mine from rs engine supplies google them for details but came in a damn sight cheaper than vw although doing research at the time i think the genuine vw shells are realy the one to go for if you can afford it which i couldnt and currnetly have some ks ones in my 1341 turbo !!
bottom end and top end gasket kits both availible from rs engine supplies erling in make which is what i used i think vw do both aswell but will again come with the larger price tag think the genuine g40 head gasket may now be obsolete aswell. think the original manufacturer was victor rienz so if you wanna go direct its worth a go for gaskets, hope this helps and good luck as it gets expensive with all bolts and pistins shells oil pump chain cam belt water pump etc...etc... oh and for the record do not get a pattern part oil pump they are crap quality go genuine only in my opinion any way.
