The 1988 Ranger was designed for smaller, inline four-cylinder and V6 engines. The 300 straight-six is considerably larger and heavier. It would require major alterations to the engine bay, including:
* Firewall Modification: The firewall would almost certainly need to be significantly modified or even replaced to accommodate the larger engine.
* Frame Modifications: The frame might need reinforcement to handle the increased weight and stress.
* Suspension Modifications: The suspension might need upgrading to handle the extra weight.
* Drivetrain Modifications: The transmission and driveshaft would likely need to be replaced or heavily modified to match the 300's different dimensions and output.
* Exhaust System: A completely new exhaust system would be required.
* Wiring Harness: The existing wiring harness would be incompatible and a new one would need to be fabricated or adapted.
While some people undertake extreme modifications to fit larger engines into smaller vehicles, the effort and cost involved in fitting a 300ci straight-six into a Ranger would far outweigh the benefits in most cases. It's simply not a practical swap. Consider a more compatible engine swap, such as a larger V6 from another Ford vehicle that's designed to fit the Ranger's engine bay.
