The stroke difference is 3/16", which lowers the reciprocating tensile stress by about 2.4%: 270, 302 etc. at 6,000 = 248 etc. at 6,146 (A=X).
The drop in power by destroking from 4" to 3-13/16" is about the same: 2.4% (using Lanchester's formula), net result is slightly less power at mid speeds, about the same at both peaks.
The rod ratio is slightly better for the shorter stroke, but it doesn't do much: 1.75:1 vs. 1.836:1.
