The reason you can't find aftermarket fuel rails for it is because it's 2022 and that garbage is no longer supported.
GM literally invented the greatest engine lineage ever, and they did it right in the middle of the GMT-400 years, there is
no reason whatsoever that anyone should cling to the trash that came in these trucks. You cannot make any argument that the 100% dumpster fire TBI crap that came in these trucks stock is worth keeping, so stop.
Throw it in the scrap bin and get an LS.
We own the best looking trucks in the history of the Chevy truck line, take the technology they've given us and run with it.
I don't want this to sound like I'm being a jerk here, I read these forums every day, and I see you guys trying to spend money to make your trucks go faster and perform better, I totally get that. That's how we all got started. But relative to the money and time you're spending, stop. The returns you will get are a waste of time. Go get a junkyard 4.8 or 5.3 and get after it!