Thoughts on moving from 5W-30 on high mileage 4200 Vortec

I forgot to mention the 0W-40 is the European formula. So one area I also wanted to learn more is the ability of the oil to get flung for lack of better terms, tonthe cylinder walls having a higher viscosity @ 100 deg C. The HTHS numbers while shown in tenths, those tenths mean a lot, and I'm assuming the viscosity values are the same. The early 4.2L vortecs to the best of my knowledge, lacked the piston squirters or improved piston squirters. So with new rod bearings on a "loose" engine where a good oil film might be desirable on the cylinders for the skirt wear...I dont want to take away too much from the ability to lubricate the cylinder walls. At operating temp, the engine sounds good, very, very faint sound of piston slap, and I'm almost positive that's what it is. Would like to understand more about the viscosity @ 100C and having too thick of an oil to possibly starve the cylinders of oil...if that's even an issue. Many thanks so far.
Today I sent out some samples to Blackstone, also two VOA's for the M1 0W-40 Euro/ M1 15W-50 mix, and the Driven LS-30. Curious as to the shear of the PUP and the M1 mix, as well as any aluminum from the piston slap. Will keep you posted.