Wandering around the road of it's own volition isn't a steering box issue so much as worn parts in the steering linkage or even ball joints (you may have slop in the steering gear but not enough for it to leave the road). If all of the parts are worn, then the additive slop can allow the wheels to wander where they will despite your input to correct until you take up the slop.
As to your question. Yes any Saginaw 600 series box (the one with the four bolts on top) will interchange with your steering gear box from 1965-through 2001. You want one out of mid-eighties and up car. The better (faster turning) will be found in sporty cars such as the Monte Carlo SS, Jeep (other companies used the same Saginaw Gear steering box even Ford), or a full size Impala police car.
A Camaro box will also bolt in place, but it will have the lighter Saginaw 800 steering gear box (the one with a circular steel plate held in with a snap ring on top). I say lighter because it has a slightly smaller splined output shaft that will require you to retain the Pittman arm off of the donor car (assumes it is the correct length Pittman arm as the Camaro has three different lengths depending upon manual, or power assist, and the base model differed from the sport variant that was manual quick turn only).