Thanks for your responses.
I booked the 65 min connection (CGR->GRU->MAO) and made the MAO flight, but just by the skin of my teeth. Who knew you had to go through customs/immigration again when coming into Sao Paulo from Campo Grande??? I'm not sure if the plane was an international flight that just stopped to pick up a few more passengers in Campo Grande, or if that area is so close to the Bolivia/Paraguay border that Brazil decided to treat it as "international" for the sake of increased safety/control.
Anyway, thankfully the lines were short in GRU, and the GOL personnel were very helpful about getting me on the flight in time. If either of those hadn't been the case, I would have missed it. By the way, checking in for GRU->MAO at the same time as the CGR->MAO flight was not possible.
Re: the 35 min connection, for future readers' reference, there would simply be no way to make that.