Big-block conversions move the ZF back FOUR full inches with no known halfshaft problems. Biggest problem for most engines is the oil pan notch vs the under-engine crossmember. But some LS engines are dry-sump with shallow pans and can mount high enough that clearance is not an issue.
As far as the 'Chevy-in-a-Ford' thing, its well known that GM "borrowed" designs from a number of sources in building the LS series engines, including the hot-rodders. Some hard parts adapt almost directly from LS to thirty-years-older 351-Cs! Just look at them as modernized Clevelands, or what Ford might have done had they not thrown the Cleveland design in the trash in '74 & kept the Windsor truck engines.