This question comes up again and again; whether to migrate I-DEAS drawings to the same Item Revisions as their related parts/assemblies when migrating TDMs to Teamcenter. The answer is, "It Depends.".
In my PLM World 2007 Presentation, "I-DEAS to NX Case Study: Preparing 5 TDMs for Migration", I cover by example the stringent requirements and pitfalls associated with trying to create order out of chaos by merging previously unpaired TDM dataset types into a common TC Item series.
For most I-DEAS customers, I do not recommend this for the reasons mentioned in that presentation.
The only I-DEAS customers that can/should migrate drawings with models in the same TC Item series are those that do not need access to previous drawing revisions/versions, and are very cautious to ensure that their TDM data will not encounter the problems mentioned in the presentation.
However, after migration is complete, the rules can be changed so that everyone can map drawings with their related models for newly created I-DEAS data in Teamcenter. This is what we did. We mapped all legacy TDM data during migration to their own Item series for historical purposes and to avoid the other problems mentioned in my presentation. Then, after everything was migrated, the behavior was changed to allow new drawings to be saved to the model's item revision going forward.