No.
This timeline on the MAF website mentions no activities in between:
Year |
Major Events |
... |
|
1965 |
MSFC Michoud Operations name officially changed to Michoud Assembly Facility. Construction of the Saturn S1B and S1C boosters continued at the Michoud facility until the early 1970s. |
1970's |
The Apollo program wound down and work began on the Space Shuttle, the next generation launch vehicle. |
1981 |
First External Tank was produced by Martin Marietta (now known as Lockheed Martin Space Systems Company) flew on STS-1 on April 12 and returned on April 14. Space Shuttle Columbia orbited the Earth 37 times during this 54.5 hour mission. First manned space flight since the Appollo-Soyuz Test Project in 1975. |
... |
|
The last S-1C stage was shipped from MAF to the Mississippi Test Facility for static firing tests in September 1970 and returned to MAF in October of the same year. It was considered for a Skylab mission up until about 1975-ish, but after completion of the stage the production facilities were no longer used.
Production of the Space Shuttle External Tank kicked off already in September of 1973. The first tank was delivered in 1979.
I have found no evidence that anything got built in the three years between finishing the last S-1C and the start of ET production.