Robert, The smaller pipes hurt a little, but unless your Mopar was specifically singled out for this restriction, everyone will have the same problem.

I can tell you that as the cubic inches increase (it won't matter if that 408 CI was because you stroked a 360, bored a 400, or destroked a 440, its still 408 CI that has to pass through the exhaust), the effect of exhaust restrictions becomes more apparent.
Higher RPM will also be more effected by exhaust restrictions. These restrictions will likely show up at the end of the straight on a circle track, and as the laps add up (unless you run a track where the off throttle time adds up to enough time to clear the exhaust buildup). An exhaust restriction also tends to push the engine temp on extreme conditions.
If you think in terms of how much exhaust has to pass through those smaller pipes, you will have a clearer picture of how that restriction will effect your goals. If you want big CI, lower your RPM range. Gene