Gen 3 Hemi doesn't fit into a-body cars very well. That may have changed, but the first guys doing it had to work at it iirc.
Big blocks don't fit well in A-bodies either with out fenderwell headers etc.. For that matter small blocks don't really fit all that well either--we have just learned to accept all the compromises. I am SURE a G3 will fit in an A-body better than any of them with fenderwell headers and with zero concerns about sparkplug access to boot!. J.Rob