Everything looks good except for the prices and the plugs. The AC Delco R44LTS6 plug is the standard plug and is what I would use. Much cheaper too. Look on Amazon.com for the others. I just replaced my coil too and i think it was 25 bucks with free shipping with Amazon prime. However, compare amazon to rock auto as sometimes rock auto is cheaper on parts even having to pay shipping. Rock Auto is a drag sometimes because they will ship your order from 3 different warehouses charging you shipping from each one.
I see now where you have the AC Delco Iridium plug, those are fine too just more expensive. Amazon has them for 4 somethings a piece.
One final thing, now that I think about it my truck (identical to yours) had the same thing kinda going on. I don't know exactly what caused it but I noticed I was losing coolant, and the exhaust smelled rich. Then the CEL came on for catalyst insufficiency. I was burning coolant due failed lower intake gaskets which may have burned out my catalytic converters, or something was going on telling the computer to dump fuel to it which could have caused it. But with 178K on it at the time. I decided I was never going to get rid of it and ended up doing the lower intake, changed the spider out with the MPFI system, and put new cats and O2 sensors on it. Runs awesome now and has for a year. The only thing I wish I had done was change the distributor gear while I had it out as they are nylon and will wear out. However, when they wear out I believe they will throw a timing code due to the +/- 2 degree discrepancy. Not sure. My point being, if you plan on keeping the truck, and know it's never had lower intake gaskets now may be a good time to do it all.