The weight of those things is always the first negative. Everything on those early motors is cast iron. But so is everything on any other "stock" motor. The only thing making those any heavier than any other motor is the larger heads. And even then, they still don't weigh as much as a gen II hemi. But as soon as you start replacing some of that iron, the weight drops significantly. Timing cover, water pump, intake, distributor ... there goes 100 pounds right there. My point is, don't belittle these motors because of the weight. The only real issue with these motors is the cost to build them and in reality, if you did a similar parts swap on any other Mopar motor the difference in cost wouldn't be that much.