What crank is this?

Correct! You would need one of the smaller cranks. Like the 3.46 crank. MP also had forged cranks with similar strokes to them to meet the 3.55 CID rule.

The 3.46 crank and a 4.04 bore it would be a 354.83 of CID.
At a 4.06 bore, it would be a 358.35