Well, the block heater completely eliminated my startup smoke, so I plug it in every night once fall comes, on a timer. Only needs a few hours.

But in terms of your situation, couple of suggestions aside from the block heater:

-have you done your fuel filter yet? Also make sure you get the air out of it after install.
-glowplugs, as you mentioned. They're easy to check visually. YOu can also try cleaning "bus bar" that connects them all together, its possible is starting to get all corroded on you.
-dirty EGR valve can also cause smoking, might try cleaning it too.

I give you all these suggestions because even if it doesn't improve your smoking, your truck will run better, and you haven't just thrown parts at it randomly.

Otherwise... how's your batteri(es) for cranking amps. Are they giving you enough juice to completely light those glow plugs? Is your afterglow circuit clicking on and off? Dirty injectors may also be a possibility...but I haven't done mine yet, so I can't speak to them...

Hope this gives you a starting point. <img src="/forums/images/graemlins/cheers.gif" alt="" />