This will likely work, barring a late incoming flight or unduly long delays with baggage delivery.

BAs stated MCT is one hour: https://naprepin.custhelp.com/app/an...rulhos-airport.

Walking or taking the bus will take an able-bodied individual around ten minutes. I do the walk from the very end of T2 to the AA end of T3 with bags and a dog in about that time. There's a few curbs to climb, so if possible avoid using a baggage cart.
Most of the time, walking is actually quicker than taking the inter-terminal bus. Just not in a downpour...

Only issue I can see: You might find you're unable to drop your bags in case you arrive at the desk with less than 61 minutes to spare as the agents manning the check-in counters have a tendency to abandon the desks at T-60. Happened to me once.