Working from straightforward concepts.
Engines are air pumps. Run the ideal amount of gasoline in a quantity of air per unit time, and a certain amount of work can be done. To do more work, you must move more air and fuel. You can make the cylinders bigger or cycle the cylinders faster or cram more air into each cylinder.
In normally aspirated gasoline piston engines, at the best place on the rpm curve for scavenging the combustion chamber, you will make about one foot-pound of torque per cubic inch. Torque will be lower at higher and lower rpm than at that best place. Run boost and it is the equivalent of running bigger cylinders.
Power is torque at speed. In Imperial units, torque (in ft-lb) time rpm/5252 is the horsepower. Just getting more power may not be much use if it is at much higher rpm.
So, if you add 0.060 over bore, the displacement goes up, and your peak torque, if it can be made to breath as well as before enlarging the bore, should go up pretty much linearly with increased displacement.
Same goes for the stroker crank in that it makes the displacement bigger. If you can make it breath as efficiently and turn as fast as with the standard crank, torque and power can increase linearly with the displacement. Usually, the increased stroke will drive the torque curve lower along the rpm band (greater energy sucked up accelerating the pistons up and down), which can be a good thing if you are trying to turn a prop - you can increase prop diameter and get better efficiency from it.
If the induction and/or exhaust system becomes the choke point for moving air, your peak torque may not increase much, and may occur at lower rpm, resulting in about the same power.
But all of this "breathing the same" and being able to spin at the same rpms, becomes moot if you can increase the density of the air being ingested. Turbochargers do this. If you put more air through the engine, torque will usually go with manifold pressure. Now the question becomes "will the pistons, connecting rods, crankshaft, and associated bearings hold together through all of that? I do not know how much manifold pressure any given Corvair engine will stand.
Going through an example... 183 in^3 is about 183 ft-lb of torque. If it makes that at 3000 rpm, that is 183*3000/5252 = 104 hp in normally aspirated form. Boost to 40" is 104*40/29.92 = 139 hp. Hmm. Looks like Ross and I do the same math, as he estimated 140 hp.
Have fun with your numbers, but remember that the entire think has to hold together at whatever power you get...
Billski