383 magnum versus 383 big block
Are these calculations taking into account the better exhaust path that's possible with the small block? Last I knew, those manifolds or headers on the big block A body cars will be compromised to clear the steering, torsion bars, etc.
It doesn't show up in the dyno numbers, but overall a LA small block will have roughly 75 less pounds to haul around than a low deck big block!
This is the very first thing that came to my mind...if the difference is only 75lbs, it's not as big of a deal as I was thinking but this is significant...worth almost a tenth in the quarter mile.
I realize that the OP mentioned that this was already a heavy car (running AC to boot) but weight and weight distribution are significant factors in how the car is going to drive.
I love big blocks as much as the next guy but I'd lean toward saving some trouble and sticking with the small block. Add in aluminum manifold, heads, water pump, some light pullies, electric fans, and you'd be way lighter than an iron head big block and you would be on your way to a better driving experience, IMO.
