Find some better cranks would be first priority, lighter will probably look after itself. 640g sounds like Italian scales for cranks + chainring, but you're still at 950g complete with BB, which shouldn't be hard to beat with external cups. Even Omnomnom boat anchors are in that area.
Find some better cranks would be first priority, lighter will probably look after itself. 640g sounds like Italian scales for cranks + chainring, but you're still at 950g complete with BB, which shouldn't be hard to beat with external cups. Even Omnomnom boat anchors are in that area.