Well no dispute on the Lt1 and ls1s dominance over mustang during those times. It's not gms fault that Ford invested in the weak n/a 4.6 for so long.
How would the 4.6 be weak if it was putting out more HP per cubic inch? (DOHC motor we're talking about here). The 4.6 has kept up with the LT/LS motor very well. There was no pure domination. The terminator ended a close battle between the two.