The engine has been run cold, and with a failed O2 sensor. Good chance that the catalyst(s) are damaged. So again...run that thing long enough to get EVERYTHING warmed-up. Maybe the catalyst(s) can come back to life again.
Replaced the two before - cat o2 sensors.
Good. Now replace the downstream sensors...they're almost certainly past their prime.
I had less white smoke after letting it run but still smells a little rich.
"Rich" does not have an odor. "Rich" mixture promotes carbon monoxide (CO), and CO is colorless and odorless. Which is why it kills people. Makes 'em sleepy with no obvious signs of being poisoned.
"Misfire" smells and has eye-watering hydrocarbon (HC) fumes.
"Failed Catalyst" smells kinda bad, has some eye watering fumes, but not nearly as bad as outright misfire. It's what all cars in good condition smelled like in the days before catalytic converters.
First Guess: You're smelling uncatalysed exhaust because the cat was damaged from previous engine problems--running cold, running rich.
Drove the truck around for about 45 minutes and not one bit of steam came out the tailpipe.
it was warm out today but I know I drove it before in warm weather and had tons of steam coming out a few months ago.
Seems like that problem is history.
Im going to throw my hat on a bad fuel filter and perhaps some bad gas?
Unlikely.
Not to beat a dead horse but still dealing with this issue and I beleive it is unburnt fuel.
If your eyes aren't watering, it's not unburnt fuel (HC).
Today I checked the plug wires and found they were in very poor shape, going to do the "tuneup" with plug wires cap and rotor. Also going to check the condition of the ignition coil.
Will the coil fire a spark-tester calibrated for HEI?
i tested the fuel pressure and its at 50psi key turn on and i am not leaking any fuel pressure. Thats thanks to a new mpfi set i installed.
As said...50 psi fuel pressure with no vacuum in the intake manifold is kinda low. Is your gauge accurate? Does it increase with multiple "priming" cycles?
Driving it now i get loads of backfiring.
Backfiring in the intake manifold is not the same as backfiring out the exhaust. Which is it?
Did you get the wires routed properly? Lots of space between #5 and #7 wires? Preferably routed EXACTLY like the service manual shows, using all the original plug-wire looms?