Soo I'll start by saying I looked through a lot of threads and found similar issues but not quite the same.

So for starters this was Grandpas truck it died on him on his way home from the dump. Limped home and parked it figured it was a fuel pump and never got around to looking at it.
Fast forward 8 years and it's still sitting in the same spot he left it.
Tossed a battery at it and a quick shot down the throttle body and she fired up. Even managed to drive it on to the trailer.

Got it home. It would run and idle pretty good for sitting in a field for years
Went to a scrap yard got a throttle body and IAC .out of a 5.8 bronco that ran fine, just had the roof and sides squished in (roll over write off)

Cleaned them out real good put it on and it ran decent. But then it would start to stumble miss and die...
Would fire right back up and go again.
30-42 at the rails. New water pump,cap rotor,plug wires , ect ,temp sender,air charge ,fixed vacuum leak s ,no holes in the coffee can.
New fuel filter...

So it runs great and can Rev all day ,put er in gear and drive. But then it starts to stumble and miss and eventually stalls.
Put in park and will fire right back up
Will drive again..... Stall.....
rinse and repeat...

Was going to change the o2 sensor but busted the Bung off oops ...

Now I'm stumped... Plugs have a nice color 👌
And I have good fuel pressure.... What could it be.....

Oh and tps tested good and rail psi his up 5psi with fpr in hooked from vacuum. And IAC unplugged lowers revs to about 600 and revs nice....

I have not touched the fuel pumps but have changed filter.....

And no I didn't just toss money at it hoping it would fix itself... I changed all the parts as a tune up/overhaul from sitting in a field for 8 years and yes theirs fresh gas tank was drained when parked...
It will start every time and idle all day well mostly
But then it stumbles , Misses and stalls. Giving more throttle doesn't help and if it doesn't stall it will stumble and idle home...

 

If it idles fine but stumbles and dies under load, it sounds like a fuel problem. It seems almost like the fuel filter is still getting clogged. In this case, you need to be able to check fuel pressure under load.

I've had to deal with fuel tanks that seemed to have an endless supply of crud that keeps clogging new fuel filters and even had really fine crud that got past two filters to get into the carburetor. I ended up flushing out the tank and fuel lines with mineral spirits and pressurized air.

The other possibility is clogged fuel injectors, but this sounds like the fuel filter is clogged again.

 

Well when I Rev it manually I get 40ish psi but that's in the driveway and in park or neutral.
it will do this tho in park or in drive... I'm kind of thinking fuel issue also .. filters cheap maybe I'll have to flush out the tank