I haven't looked much into the aftermarket, but a quick google search revealed this:
Vehicle Platforms | XLHybrids
Looks like it goes in-line with the driveshaft, but I can't tell if it has an internal clutch. If we assume it does, then the engine can be disengaged and you can creep along in stop and go traffic using zero gasoline (no fumes) and without any clutch wear or hitting your bearings over and over. When you pull away from a stoplight or are going up an on-ramp, the electric motor bump starts the gas engine (no starter, saves weight and is one less part to fail) and gives an extra 220ft-lbs of torque (from zero RPM) on top of what your engine produces to accelerate. When you get up to speed, you can either run on gas alone, or electric alone, or use both together when you want to pass. You can use the electric motor to brake the car, which prolongs brake pad life and puts your kinetic energy back into the battery, to be used to accelerate again later with zero fuel used. You can get rid of your alternator (saves weight, one less part to fail) and instead use a highly efficient DC-DC converter and a downsized 12v battery (lawnmower or motorcycle sized) to power the 12v components in the car.
It does add complexity, but it also subtracts complexity. By assisting the engine, you prolong its lifespan - there are examples of 400k mile Chevy Volts and 600k mile Insights and Priuses on their original engine, still running great.
Maybe it would be unreasonably expensive, but frankly I don't know how much the costs of your proposed engine modifications would be, and it might not be dissimilar. I expect you'd get both more power and more economy by putting an electric motor in the middle, and you'd still have your high strung V8 noise, too.