Doing some OOB research.  >>/36415/ lists the 2nd Infantry as having two battalions but elsewhere mentions it only had one. I looked up the source (Army Reserved Bulletin 11-C, 1970) in the National Archives and indeed it's only one. But there's more, it breaks down to the company level. For instance, the Infantry-School Regiment had:
Commander & staff
Command company 
Services company
Hvy mortar company
Tank company
x2 Infantry battalion
Commander & staff
Command company
x3 Fusilier company
Hvy weapons company

Most others have no heavy mortars and merge command and services companies. The number of fusilier companies per battalion varies, two-battalion regiments often have two-fusilier battalions, so those are a better yardstick for comparison.

The Tiradentes Detachment had 8 (Army) and 6 (Police).

1st Caçadores: 2, possibly only one at the frontline.
1st Infantry: 2 assuming one battalion stayed in quarters.
2nd Infantry: 3. The engineer company following would also man the frontline.
3rd Infantry: 4, but how many in theather? At the very least one battalion was on its way.
Nonetheless sources still state Cunha Melo had the numerical advantage over Muricy.

AMAN Cadet Corps: 1-1,5.
AMAN Command and Service Battalion: 1 (guards).
1st Armored Infantry: 2.
5th Infantry: 3.
6th Infantry: 3.
4th Infantry: 4.
1st Light Tank Battalion: 2.
4th Caçadores: 2.
17th Cavalry: 2.