Your best bet for a relatively straightforward swap, though not strictly "bolt-in" without some adaptation, would be another TH200-4R. You'd need to ensure the transmission is from a similar-year GM vehicle with a similar engine to minimize compatibility issues. Differences in bellhousing bolt patterns are rare but possible across years, requiring a bellhousing change or adapter plate.
Other transmissions *could* be adapted, but it would require significantly more modification, including potentially changing the torque converter, driveshaft, and potentially the crossmember. These modifications generally aren't practical for a DIY project and are better left to experienced transmission specialists.
In short: Stick with a used TH200-4R from a similar-year GM vehicle. It will be the easiest and most cost-effective option. Look for one from a Buick, Oldsmobile, Pontiac, or Chevrolet vehicle with a V8 engine from the same era. Before purchase, carefully verify the bellhousing pattern matches your engine.
