How to identify the Employer, EIN and Plan Number of a 401(k) Plan aft

[Guest EMC]

After Company B has merged into Company A (i.e., Company B no longer exists) and has "frozen" contributions to its 401(k) plan as of the corporate merger date, does former Company B's "frozen" 401(k) plan subsequently report under Company A's employer name, EIN, and next available Plan Number between the corporate merger and the ultimate plan merger (since Company B no longer exists)? Plan contributions continued seamlessly for the employees of Company B into the Company A 401(k) Plan.

The specific situation is that Company B's 401(k) Plan has some operational defects which must be corrected under EPCRS prior to a merger into Company A's 401(k) Plan, and so there will be a period of time when the 2 plan co-exist. Company A would like to shift the assets of Company B's "frozen" 401(k) Plan onto the same investment platform as its 401(k) Plan is on to allow the employees to have the same investment options. Unfortunately, this requires an amended Adoption Agreement (the Co. B Plan is currently on an insurance company Adoption Agreement, which must be changed if investments are shifted our of the ins. co.'s investments). On the amended Adoption Agreement, the "Employer," "EIN," and "Plan Number" must be identified. Do we use Company A's information, including assigning the next available Comapny A "Plan Number" to the "frozen" Company B 401(k) Plan?

Any suggestions or thoughts are appreciated.