2. yes, they are, but the V8 crank (and block) are inherently much stiffer (less subject to bending and misalignment) than an L6.
3. IMHO yes, very smart guy, the choice for NASCAR might be the other way
I don't think that it's an accident that some of the most successful turbo engines developing extreme power (1,000+) with the original block and crank have very stiff cranks:
1. Buick OHV 231 V6 (GNX etc.) - 4.24" bore pitch
2. Toyota 2JZ-GTE - it's an L6, but the crank (and block) is extremely short - 3.622" bore pitch with 3.386" bore!
3. Nissan GTR 3.8 V6 - 4.409" bore pitch
Crankshaft length is critical to stiffness (although this can be somewhat offset with very large journals), which is why L8 engines were never successful with any power - too flexible.
For comparo, the length of a crank (#1 to last main bearing) is roughly the bore pitch X number of cylinders in one bank, + 1 rod width if a "V" engine.
You can see immediately that a V4 would be best (but very limited displacement), V6 next, then L4, V8, L6, V12 etc.
