Reminds me of my '97 K2500. Bought it between Christmas and New Years, just over two years ago. Ran like crap. No lockup. Enormous misfire count on #8.
Had multiple other problems as well, but the misfires and the bum torque converter were my real concerns.
Got it home. Decided to compression-test #8 to see if the engine had to come apart. Loosened the spark plug with the socket and ratchet, then reached down to twist it out by hand. The moment I felt the plug, I knew it had a cracked porcelain. Compression test came out OK, I poked a used spark plug I stole out of a spare engine (correct heat range and reach), and the misfire was gone. Torque converter clutch worked, too--because the Computer disables the TCC when it detects misfire.
One spark plug fixed the misfire AND the torque converter clutch. That was a good day!
