look very closely, I want to point out a few things and dispell a few myths, first, that those 215cc heads don,t seem to hurt the torque much on that 392 small block now do they?? in fact if you look closely the differance in the peak tq was only about 15 ft lbs and the larger heads made more tq, (but at about 1000RPM higher) and most of that change in rpm level was due to the change from dual to single plane intake manifolds and a shorter crank stroke!
second, look how those fuelie heads kill performance on that second engine, and third notice how the single plane intake and shorter crank throw moved the torque peak higher in the rpm range but the peak torque remained high. and yes they are not similar engines in many respects but none the less thats very impressive power from a small block.
third, notice the heads,cam and compression matched to an intake that flows about 275cfm is necessary to make that power,keep in mind the stock TPI intake flows in the 200cfm range, effectively strangleing the corvettes engine, thats why why I keep adviseing swapping to a custom stealth ram,on the corvettes or standard stealth ram EFI on cars with hood clearance to gain flow on similar TPI engines!
and YEAH THOSE ENGINE NEED RACE GAS AND WON,T PASS EMMISSION TESTING