For the most part, I'd base my decision on what engine you want to have in the vehicle.  If you rebuild the M110, it will go a very long way no doubt.  I would venture to guess that it will go a fair bit further than a donor/original 617A.  Most of these engines, while still very good, are getting a bit long in the tooth.  To rebuild a 617A will be a costly undertaking as well. 

Now, if you have been thinking about converting to a diesel anyway, then this is a great opportunity (possibly your only reasonable opportunity). 

A few words about the "car" automatics.  First off, do you currently have an auto?  If not, you have many parts to buy to convert; not a problem just think about it.  If you do have one, your G tranny will be better as it is stronger, has lower ratios, is more waterproof, etc.  If you want more on this, PM me.  However, the problem with the 280 auto and I think most of the "car" autos are that they all start in 2nd.  Take an engine that is a dog below 1500rpm and add a second gear start to this, and its very slow off the line.  This is where a manual will be better.  The other problem is that with 32" tires, a 4.9:1 r&p, and the auto, you are at about 4000rpm at 70 mph on paper.  Add in a torque convertor that, albiet has very little slip at this speed but does have some none-the-less, and you are at over 4000rpm on a diesel.  That sucker is loud and your fuel savings goes out the tail pipe:banghead:

I don't want to discourage you, just think that the MB engineers geared all of their turbodiesels much higher (350GD= 4.11:1 r&p and 1:1 4th; 290GDT= 3.72:1 r&p and 1:1 4th; the rest of the 463 series had an overdrive TC, usually higher r&p gears and an overdrive tranny).  With a 617A in there reving that high so much, be sure you monitor your EGT and possible take precautions by putting in higher gears.  This being said, others have had success with their swaps and like them very much.  I have also talked with many who are not happy with them.

Sorry this is so long and rambling, I just want you to think of your options considering other factors.  I have a 617A and auto and I like it but do see some problems.  I drove a 280 with an automatic and liked it much more for urban driving than my diesel.  If my truck had higher top gears (overdrive or r&p) I think it'd be perfect on the highway but even worse in the city due to the 2nd gear start.  I'd have to make it kickdown at each start which yields a much faster start.

 Steve

Exchange crank and bearings for M110 from Metric Motors = $730

http://www.mercedesengines.net/proddetail.asp?prod=280recon

If the problem is the small end of the rod, less money to buy just a replacement rod of the correct sizing and weight.

Remember that any 617A you buy will be an unknown quantity.  People who bought them (used 617As) and got LESS than promised far out number those who got more.  If I were you, I'd plan on spending $2-3k on any 617A you're going to buy, either right off, or in the forseeable future.  Like Steve said, they're getting tired.

As far as performance goes, there's no free lunch.  Basically the VG080 transfer case in the 460G won't take much more power than the M110 gives out, so even if you have it at your disposal, it'll be wise to take it easy with the right foot.  I was really THRILLED with the power I was getting from my 617A, till I found out that if I kept using that power, I'd smoke the turbo and exhaust valves before long.  Now that I'm back to keeping EGTs under 1200 as folks who know about these things recommend, I find the power very comparable to my M110, just available in a different part of the rev range.  Meaning I can do hills at lower revs in 4th gear that my M110 required winding out in 3rd to make the same forward progress.

What I did get, is exactly what I was after.  Better driveability - being able to run a gear higher most of the time, and better fuel economy (19-20 with the 617A vs consistent 12 with the M110 in my driving).  I also got the benefits of turbo helping at high altiudes where I drive all the time, but that's not super significant, except as results in the driveability mentioned.

But aside from those two, there's not much difference.  My 460 was never particularly fast, and it still isn't, and I don't care about that.  I got what I was after.

I have the "donut" type motor mounts, and I didn't have to move anything on the chassis to make the M110 to 617A swap when I used motor arms from a 300GD with donut engine mounts (but I hear these are NLA).  I don't know anything about having to move a portion of the chassis motor mount.  Warren mentioned it to me in a conversation the other day, but I was a little baffled.  A check of the chassis part numbers for 300GD vs 280GE in the '84 type vintage would provide the last word.  Glow plug light is the least of your worries.  It's just an output from teh glow relay.  Put a light anywhere you like.  For some reason my truck had a "seatbelt warning" lamp to the left of the temp gauge, so that's my glow light now.  Some day I'll figure a way to transplant the orange lens with little "fillament" icon from a spare GD instrument I have, but I'm not in a hurry.  You don't really need the light as you can hear teh relay "clunk" when it's done.  But the light is nice for diagnostics as it flashes if a glow plug goes out.

ARB mounts are on their way to Steve's shop.  Shipped last Friday.  I need $120, total parts and shipping, between the two of you.  You guys gan fight over how to split it.  :^)

All the best,

Dave G.