I picked up my rebuilt axle's today for the '83 300d....it is a different style of axle the the previous one, but I was told it would work. The "new" one has the bolts all around the inner driver and seems to be a bit sturdier then the one originally on the car.

The spacer ring that came off the old CV's don't seem to sit flush against the inner driver shaft on the new axles, and with the spacers on, I can't get the clip on the axle in the differential. It all fits together fine without the spacer rings on at all.

What happens if I just leave the spacer rings off? I'm thinking with the different axle design these spacer rings wouldn't work anyway.

I believe the spacer is there to allow a means to compensate for variances in manufacturing of the parts. If you are getting the proper clearances without the spacer you do not need it. However, I do not know what the proper clearance is. Please see if you can find the proper clearance at this site:
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/Main.html

Annular type axle has the bolts around the CV joint on the wheel end and I believe a 12mm bolt that goes through the wheel end (the one I believe you have).
Homokinetic typ axle has what I call 2 "cans" and I believe an 8mm end bolt.

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84 300D, 82 Volvo 244Gl Diesel