A friend of mine uses the Sierra 1.8 crankshaft with forged Wiseco pistons in his 1.6 turbo block. Compression about 8.5:1 and up to 300 hp, 1.5 bar and 7000 rpm. Had no problems yet. Engine was bored out to 81.5

The 1.8 crankshaft fits the block, you just have to do some work on it to provide space for the conrods because of the higher stroke. Didn't ever see a crankshaft that didn't cope with the power. It has always been melted pistons, bent rods, worn bearings but never the crankshaft...