Well time for an update...
It was tough getting the front main seal out due to the gasket cement they used but I got it out. Then I found a significant problem. The spacer ring was broken; it actually looks like a piece was missing. I hope it didn't do much damage clunking around in the engine. I'm planning to drop the oil pan to replace the gasket; maybe it will be there. I'll post a pic of the broken part. Makes me glad I went the extra step of replacing the main seal. I used the whunter cup tool method described in the DIY Section; it worked great and I would have screwed it up if I hadn't read the article.
I ordered a used harmonic balancer. The old one was pretty "wollered out". The crank shaft felt like it was in good shape--no noticable rings or wear. I guess the softer balancer absorbed all the wear.
I've read a number of posts on aligning the dowels and will do that part this weekend. I have four sets of dowels on hand in case it take a few tries. FYI--the new dowels from MB are beveled on both ends and seem to be of a higher grade. They're kinda yellow like Grade 8 bolts.
I don't think I'm going to use Loctite on the 18mm bolt, probably just Antisieze. I'm planning to use assembly grease on the dowels but I'll use Loctite on the capscrews that hold the pulley on.
I've been trying to locate a big torque wrench; mine only goes up to 150 Nm. I'm thinking about using my 18" breaker bar and my 200# body weight. That should get it close to the 270-330 Nm spec (1.5ft X 200lbs=300ft lbs = about 400 Nm). Then I can go to a shop to check it.
Updates to follow...

If there's enough room for it, it might be better to use a torque multiplier rather than buying another torque wrench.
Not sure I like the idea of antiseize as opposed to Loctite since there are accounts of that bolt coming loose.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I appreciate your concern and thanks for the links you provided. I'm thinking of going with the antiseize for three or four reasons:
1. The MB manual says to lube the 18mm bolt
2. I'll need to go to a shop to verify the torque and that would break the loctite seal. Plus the rotation of the engine would tend to tighten rather than loosen the bolt (or "screw" as the Germans call it lol).
3. I think most of the failures are due to the bolt not being tightened to spec or something else going wrong.
4. And the biggest reason--the Germans tend to over engineer things. If an 18mm bolt torqued to 300Nm with three cup springs comes loose, there is probably a reason. Even though the big bolt coming loose would be bad, I think a glued in big bolt coming loose would compromise the "if something is going to break, make it the less expensive parts" principle.

Number four is just a big assumption on my part but comes from a good number of years working on different types of German built equipment (mostly lab equipment). But one thing seems to remain constant, if they designed something a certain way, there were several good reasons.

Of course, I could be talking out my ass and would appreciate "been there, done that" advice.

Again, thanks for your help; I'm certain I would have been chasing my tail over this one if I had had everyone's help.

Any other input?

one word, Loctite.

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Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

Isn't the entire reason you're doing all this because the pins shattered and allowed the balancer to get all loose on the shaft nose? Loose parts, especially loose parts under force, tend to chew up everything they are loosely attached to as well as themselves. Whatever you decide, you don't want this thing coming loose until you intentionally want it removed.

The grease reduces thread friction allowing you to get the desired thrust force via the spec'd torque. The loctite will also act a somewhat of a lubricant until it sets, so you'll get clsoe to the desired thrust force, but then it'll set and raise the thread friction even higher, preventing the bolt from backing out. Just make sure the threads are clean of old grease and oil if you use it.

Me? I'd use the thread locking stuff.

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

Just one problem with going to a shop. Once you reinstall the vibration damper and pulley, you can no longer access the slots in the balancing disc to prevent the crankshaft from rotating. So it would be a lot easier to torque the bolt correctly the first time.