HP gets the credit and Tq does the work. The 5.4L is "behind"? Neither the 6.0L or 5.7L enignes have variable cam timing, looks like it's ahead to me. If you buy a pickup for TOWING based only on the PEAK HP ratings, well you aren't the market Ford is after. That must do a lot to explain the sales leadership of the F-150 for the past 30 odd years.
ROFLMAO! Have you ever pulled 6,000# with a "big block"? Those "big blocks" you think are so powerful made about 260 HP and 340 lb-ft of Tq input at the transmission. No one in 1977 thought that pulling a 6,000# trailer with a 3500 and 454 was "underpowered" and LOTS of people opted for the smaller v-8s because they recognize that they really only need the bigger engine 2 or 3 times per year.
There isn't a 1/2 ton pickup made that doesn't do a BETTER JOB towing than those old 1 tons did, and engine ratings are not a huge factor in that.
BTW, I've pulled 12,000# with 3/4 and 1 ton trucks and a "300-6" safely and for long distances and similar loads with F250 Power Stroke diesels. Both get the job done but one truck costs twice as much as the other.