GG FSE 450 crank shaft and other parts [rebuild]

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Hi! It's my firts post here. In the beginning I'd like to sorry for my grammar, I'm from Poland and if something will not look clear, just tell me.

I'm going to rebuild my GG engine. It's quite hard to get parts in my country (used/new - same problem) so I've got some questions. Btw it's FSE 450 from 2003 (supermoto).

I heared that i can use some parts from DRZ 400. Which ones exactly? Cam shafts, valves?

I'll probably have to change crankshaft and that's a big problem. It's not possible to buy it in Poland. I tried to find one on ebay but there's only one from GG 400, and the question is if it fits the 450 engine? What are the differences between 400 and 450?

Cheers