You know what kevin, just do it.
The thing will run without it, the mount wont break off, no binding/smacking when you launch full bore from a stoplight because you resent being passed. But that's it; that's the limit of the 'benefits' you'll receive from re-designing the Chrysler engine compartment, because that's what you're doing; you've told generations of superbly qualified engineers to stick it in their ear, you know a better way to do it. Of course, all the experts in the HOT ROD/Musclecar books say solid mounts are a wizard idea, along with super coils and yellow wires itty-bitty fan pulleys and all the other bitchin' tricks that made them rich and famous as builders of fine automobiles. What? Oh.
You are right though; those cracks arent magically going to appear overnight because you launched hard once, or twice, or three times. So feel free to do it your way and in a few years when you quietly discover said cracks and take your car to a welding shop to have it fixed, we'll all turn our heads and pretend not to see a thing. It's just easier that way