No doubt more power would add to the fun factor.

But it's not just a matter of dropping the Hemi (now THERE'S a modern piece of machinery...) into the engine bay, even if there is the room.

The added weight would dramatically alter the handling characteristics that are so much a part of the charm of the car, meaning the entire suspension would've needed to be designed from scratch. Ditto the brakes.

Because DC did not have to start w/ a clean sheet of paper in terms of running gear, it was able to come up with a uniquely styled, adequate performance for most folks sports coupe that can now easily be had new for under $30K.

Had they dropped the hemi in and started from scratch in all the rest of the running gear, this car would've likely been well over $50K. Which is fine, but at that price I don't know that it would've sold a whole lot better even with the extra punch.