Upon re-reading this post, I'd think it may be advantageous to have the system scanned.....or at least cycle the key for a trouble code. It's probably going to come up with a code 51 or 52 anyways ...O2 going rich or lean...but that could be the result of whatever's causing the system to puke black smoke....not the O2 itself.
383Man could be right....the temp sensor is important....otherwise there is something else telling the system it needs fuel...i.e. a lower than normal vacuum signal. That's why I suggested the EGR.A stuck thermostat will only cause the truck to get crappy mileage...not cause smoke.
A scanner will show a poor vacuum reading from the MAP.
I'd be checking it for sure.
Oh...and an OBD scanner won't do....you'll have to find someone with the proper 6 way plug-in cable for the older Mopars or go to the dealer and they'll use the DRB scanner.
66 SATELLITE 426 HEMI
71 CHALLENGER 496 6PAK R/T
68 GTX 440 AUTO
92 Ram 4x4 CTD
54 DODGE 1/2 ton PU
New best of 6.75 103.80 MPH in the 1/8th
And 10.86 122.04 MPH in the 1/4