Engine combo... need some advice please

[fast70]

The biggest without clearancing is 76mm although a 78 will fit with just minor clearancing. The stock crank is forged. To be safe, if you are comming anywhere near the HP threshold number, I would go with forged. It is cheap insurance. I have a friend who made the mistake of buying a cast crank and has had to have the crank turned down twice with only a couple thousand miles on the motor. So even though it is not that expensive to have turned:
1. It weakens the crank even farther
2. By the time the cost of the crank and cutting are added you have exceeded the cost of a forged crank.
3. Each time they need to be cut, the motor has to be torn down and new oversize bearings bought. So factor in the cost of a couple of sets of bearings.
4. You are taking unneccessary chances and stretching the rubber band to save a few bucks.

fast70