Thats a 32 valve non-VCT engine, not comparing apples with apples. The OHC 5.4s, particularly the 3v's were built super tight and with very narrow oil passages to the cams. Additionally, the piston rings actually rely on 20 weight oil to help keep things sealed up.

Viewing a thread - 5w-20 engine oil in Ford 5.4 Triton?

I can post more if you'd like. I'm certain you wont kill your 5.4 feeding it a diet of 40 or greater weight oil but the possibility of starvation is increased, with the likely result of a shortened service life. Most of these motors are capable of 300,000+ miles with routine maintenance, I would opt to put up with a little phaser noise myself.
Just sayin'.