61 Polaras have total contact brakes that are a self energizing type to reduce pedal pressures and generate more forceful braking. That design brings with it many drawbacks. If a vehicle has been sitting in a humid climate or just sitting a long time at all, the brakes will become touchy and lock up when you apply them when moving forward. The only way to reasonably release them is to just back up. But as soon as you apply the brakes again when going forward, they will do the same thing. Also, adjusting those brakes is unique and you need to read a service manual to get it right - the rears are not adjusted the same way the fronts are. Assuming the brakes will release when backing up, you should remove the wheels and then sand the brake shoes to remove the accumulated rust debris and then they will likely function OK again. Of course getting the rear drums off is always no fun on these models since they have tapered rear axle shafts whereon the drums are secured on with a large nut. They are a ***** to get off under normal circumstances as it is, so be sure to get a good special tool to remove them. The factory puller was not very good but there is a guy on the Chrysler 300 Club International, Inc that makes a special tool that isn't that expensive and relatively effective compared to the factory tool since the better tool more evenly spreads out the load when removing the drums.
One option is to replace them with regular drum brakes from a later model year full size Dodge, Chrysler or Plymouth that has regular drum brakes standard - total contact brakes went away after the 1962 models, so getting a brake set up from a later model full size car would be preferable since all you problems would go away. You could also install disc brakes from a couple of vendors and have an even more reliable system, but that is a more expensive proposition. The effectiveness of the disc brake setups that would work with your factory 14" wheels are really no better than the drum setups since the rotors are constrained in size compared to other rotors available with 15" wheels for example, but going to 15" wheels means you can not use your factory wheel covers if that is important to you. But disc brakes are substantially more reliable, thus safer than total contact or drum brakes.
