1. Engine Mounts: The engine mounts for the 22RE and the 6-cylinder engine are different, meaning you will need to modify or fabricate custom mounts to securely hold the new engine in place.
2. Transmission Compatibility: The 22RE engine typically comes mated with a specific transmission. Swapping to a 6-cylinder engine may require you to change the transmission as well, as they may have different bellhousing patterns and input/output shaft configurations.
3. Engine Wiring and Electronics: The 22RE and the 6-cylinder engine likely have different wiring harnesses, sensors, and electronic components. Integrating the 6-cylinder's engine control system with the existing wiring and electronics of your vehicle may require extensive rewiring and modification.
4. Exhaust System: The exhaust manifolds and the entire exhaust system may need to be modified or replaced to accommodate the different engine configuration and layout.
5. Fuel System: The fuel delivery system, including the fuel lines, fuel injectors, and fuel pump, may require modifications to work with the new engine.
6. Cooling System: The cooling system, such as the radiator, hoses, and water pump, might need adjustments to ensure proper engine cooling.
7. Driveline and Driveshaft: The driveline, including the driveshaft, may need modifications to match the different engine and transmission setup.
8. Frame and Body Modifications: Depending on the specific 6-cylinder engine you choose, there could be space constraints in the engine bay, requiring body and frame modifications to fit the larger engine.
9. Emissions Compliance: Swapping the engine may affect your vehicle's emissions output, and it is essential to ensure it complies with local emission regulations.
Considering these challenges, replacing a 22RE engine with a 6-cylinder in a 1993 Toyota pickup requires advanced automotive skills, fabrication capabilities, and knowledge of the specific engines involved. It is generally recommended to consult with experienced mechanics or engine swap experts before undertaking such a project.