Same Three-Digit Plan Number for two different Plans of a Sponsor

I have a new client referred to me by a CPA.  Two TPAs ago, they were filing a Defined Benefit (DB) Pension Plan (Plan #001) and a 401(k) Plan (Plan #001 (should have been #002 based on effective dates)) for the same Employer/Plan Sponsor.  The DB plan terminated and was distributed in 2016.  A final 2016 filing was never completed.  Filings for 2014 & 2015 were never filed for the 401K Plan.  I'm thinking that we probably need to amend the filings for the 401k Plan as #002 (and plan document) to get the system cleaned up along with the 3 delinquent filings for the two plans?  Would y'all agree?  Thanks.

A final filing needs to be filed for the DB plan to avoid letters from the IRS

The 2014 and 2015 filings need to be done for the 401k plan using 002 as the plan number.  Then the 2016, 2017 and 2018 forms need to be amended using the correct plan number and with Item 4 completed to show what was used before.