Mugen MBX6 V4 conversion - gears suggentions, need help!!

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Hi guys,
I'm completing the V4 conversion for my MBX6, and I have 3 questions to those who already have such an experience in the following issues:

1) if I will use direct traction with std.pinions, should I use the long shank ones with V4 conversion kit, or standard lenght?
2)Is it possible to try to use the Mugen 48T central spur? Will I have enough space between the components according to you??
3) Which kind of pinions' teeth number do you suggest for 4s batteries (under 5000mah/30-40C) + motors under 2000Kv + 46T-48T central diff Mugen spur??

Thank you very much!!!