Voluntarily giving up 42ci is sick (IN A BAD WAY) to me, supercharged or not.
That indicates to me that you are pretty much clueless about forced induction
in specific and engine design in general
Airflow generates torque.
Torque at rpm makes power.
Less displacement allows FAR lower compression and thus far more boost(mechanical comression is the enemy of boost)
Giving up 42CID is literally trivial when considering that the engine in question would be run at TWICE atmospheric pressure.
the shorter stroke would allow the engine to be more "Revvy" like a 2.9
the 4.0 is not dynamically stable above 4500rpm
and what limits the 2.9 is it's breathing.
So you'd have the revability of the 2.9 with the breathing of the 4.0 heads
not to mention the taller block which would allow longer rods
Quite often displacement causes more problems than it solves.
In this case the major limiting factor is how much torque you could force through the gearbox (gearboxes only care about torque) before it would break.
Like when I was playing with my Saab I could have increased boost, instead I ported the hellout of the head put a fairly long overlap cam in it, retarded the cam timing and went for top end power.
Why? because the transaxle would tolerate 225-250ft/lb of torque.
PERIOD, so I decided that 220ft/lb of torque at 4800rpm was far
better than 220ft/lb at 3200rpm.
Bear in mind that this represents a near doubling in power,
WITHOUT grenading the transaxle.
How much is enough?
IF you cannot get it to the rear axle, let alone to the ground,
it's pretty much not worth having in the first place.
Boosting a 4.0 would generate more torque but it still
wouldn't be able to rev without tearing itself apart.
and would do a better job of converting transmissions to schrapnel.
Even at the lower boost that would be possible in a full size 4.0.
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