My point was that there is no place on the block to act as the upper half of the extra main bearing supports. Seven main L6 engines have a bulkhead in between each pair of cylinders.
I assume the new crank will have an extra journal bisecting the existing counterweights where needed?
The bore pitch is staggered (common practice at the time), and larger between cylinders #2-3 and 4-5 than between cylinders #1-2, 3-4 and 5-6, perhaps 4.375 and 4.5625?
