Greetings
As far as I know 1.PzJgAbt.90 had 9 Marder III 7.62cm (r), 2. had 9 towed 7.5cm PAK and 3. was the former 3.Flak-Abt.55.
However StuG.Btie 90 (with 90th Light) apparently had 4 F/8s (2 had been sunk in transit) and was the redesignatioed 1.StuG-Abt.242, the rest of the Abteilung being transferred to Russia in December 1942 (source:
http://sturmvogel.orbat.com/stug.html).
Regards
Edward