Some are.. but most aren't.. Just like there's a few "outspoken" folks on this site, there's just as many on the Lightning/Harley sites.. 
The truth is.. we have to be inginuitive, just like you guys.. because, honestly, there's just not a lot of aftermarket parts for these trucks.  Outside of companies like JLP, WMS, etc.. no one is really picking up this outdated platform.  
BTW, there's a few 400-450hp N/A Cammer 5.4's out there.  
  Granted.. 4 valve heads in stock form flow decently.. but, you guys definitely have the better heads if you're comparing LSx versus 2, 3 or 4 valve Ford modular heads.
Travis