Heck, no, Spot. Not unless you have the wrong heat range in there for the type of driving you're doing. More high-speed needs a colder range, and if you use a hotter plug under those conditions you risk engine damage.
If you have a 12V system, consider electronic ignition. That would help some, but as Dale said, final drive ratio is the big thing.
What tires do you have on there now? On my 3800 I'm running 235/80R16's with my newly installed 4.10 rear - same old direct-drive transmission - and I am well pleased.
