thatmguy,
You are correct. If you have a destroyed, as in unable to repair, pre-ban(emphasis added) magazine body that came from a complete pre-ban magazine...You can replace the magazine body to ensure the specs and servicability of the magazine. (IIRC, you can use a post ban marked magazine body, but you would be playing with fire as you would have to PROVE you used the Post Marked mag as a REPLACEMENT PART) It would be advisable to ensure that any post ban manufactured REPLACEMENT body have NO MARKINGS signifying it's post 94 manufacture and that the pre-ban body which is replaced is destroyed beyond repair and RETAINED AS PROOF of the REPLACEMENT. Also, as a side note, AFAIK- there are no "Post ban replacement parts" that are marked as "post ban" by date or as "restricted")
JustL00king touched base on using a "Post ban marked body" but I feel he mis-interpreted your question. Post ban manufactured REPLACEMENT bodies have been available without date of manufacture markings for some time. I would not advise using magazines and or bodies that are clearly marked with a date stamp, ie. 9/98 or post September 94' and/or "RESTRICTED MILITARY/LAW ENFORCEMENT/EXPORT USE ONLY".
The trick is to find a supplier for the replacement bodies. CMMG, a dealer here on the site, had some for sale months ago. They depleted their supply and last I heard had found another source and expected to offer replacement bodies after the first of the year. I hope they are on schedule since replacement bodies are a necessity as the years of use continue to ravage the supply of Grand-fathered pre ban mag supply.
Take care and hide what you can't take care of...
Sly