You'll need a much stronger transmission. Good options include:
* TH350 3-speed automatic: A very popular and readily available choice, strong enough for a 350 small-block Chevy. Relatively inexpensive to find and rebuild.
* TH400 3-speed automatic: Even stronger than the TH350, better suited for higher horsepower and torque applications. More expensive and heavier than the TH350.
* 700R4 4-speed automatic overdrive: Offers better fuel economy with its overdrive gear. Requires more modification to fit and may need a custom driveshaft. More expensive than the TH350 or TH400.
For manual transmissions, you'd be looking at something like a Muncie M20 or M22, or a Borg-Warner T10. These are stronger than the original transmissions, but require more skill and knowledge to install and operate. They are also becoming increasingly rare and expensive.
The best choice depends on your budget, driving style, and desired performance level. The TH350 is a good balance of strength, cost, and availability for most applications. However, you'll need to ensure you have the proper torque converter for your specific engine and transmission combination.
