* Year of the vehicle: Bolt patterns and sizes changed over the years for various Chevrolet models using the 350 engine.
* Specific transmission: Different transmissions (e.g., TH350, TH400, 700R4, 4L60E) have different bolt patterns and sizes.
* Transmission adapter plate (if used): If an adapter plate is used to mate the engine to the transmission, it will dictate the bolt size.
To determine the correct bolt size, you must consult:
1. A repair manual specific to your vehicle's year and model: This is the most reliable source.
2. The transmission's installation instructions: These should specify the correct hardware.
3. A parts catalog for your vehicle's year and model: This will show the correct part numbers, from which you can derive the bolt size.
Trying to guess the bolt size is risky and could lead to damage to the transmission, engine, or bellhousing. Always use the correct hardware specified by your vehicle's documentation.
