I have a 1999 K3500 4x4 extended cab and 8-foot bed dually, with a 6.5 diesel. The vehicle got a dose of bad fuel a long time ago, I have managed to get that issue resolved but it's smoking white on start-up. So, I have started changing glow plugs. I have eliminated the obvious possibilities of water in the oil, cracked head, etc. So, here's what's happening.

Once I got into this, I realized that only 3 glow plugs were even connected. Not sure they were working either. Started on the driver's side and replaced the front two without issue. The 3rd and 4th on the driver's side both have the following issue:

When I put the socket on it and give it a twist it feels like it's turning, however, when I reach in by hand the only thing turning is the 6-point part of the plug (Collar maybe?) just spins. Holy moly this kinda freaked me out. But I didn't force things. Tried the 4th and it did the same thing.

I have managed to replace 5 of the glow plugs so far and have reconnected all of them to the relay. This reduced the white smoke dramatically. I can start now and let it idle for a minute or so and its clears, unless I punch it. After is gets up to operational temp it's fine.
Not sure how I'm getting them out unless I tear this down and drill them out.

Of course everything else would need to be upgraded if I tear this motor down.

I bought this truck new and it's got around 220,000 miles on it.

Suggestions?

Thanks,
Dave