103.25 x 83 mm gives 4170 cc - 4.2L - with large bore and valves, short stroke, stronger crank, higher revs, long rods, less side loading. there would be a bread and butter 3.6L, and a s.h.o. 4.2L.
with twin port/3 valves, even the 3.6 would have two 1.50" intake valves, and 1.60" exhaust; similar flow with the L92 heads. the big bore engines could get 1.55" intakes, and 1.625" exhaust valves. that's better than a 2.2" intake valve
ported lt5 heads flow 400 cfm with 1.54" valves. the poor stage 2 buick had to make do with 2.125" intake valves, and ~340 cfm
gm could employ a vtec-like system to deactivate one intake valve at low rpm. one valve would still flow 165+ cfm, but with a tiny valve, for more low end torque. it would use longer duration than the 6.0L cam. open up the second valve after 3500 rpm and get all 330+ cfm. even the 3.6 would be capable of 320+ hp. the 4.6 would exceed 400 hp. electric cam phasing would flatten and broaden the torque curve (and work upon startup in freezing temps).
the v6 can have a higher specific power output than the v8. the v6 have shorter cams for less valve action 'scatter'. it's important that the valves open/close at the same time for each cylinder. the plenum is shorter for more equal cylinder filling. a single carb version will always have more even flow, and the runners will be closer in length than a v8. the power pulses are evenly distributed to take advantage of divided intake plenums and dual scroll single turbos. and the v6 has more main bearing area per cylinder than the v8.