Will a 2001 318 cu in engine work 1995 Ram 1500 truck or will you have to change Manifolds?

A 1995 Ram 1500 likely came with either a 318 or a 5.2L (which is the same thing, just metric displacement). Therefore, the engine itself *should* bolt in. However, you'll need to carefully check a few things:

* Engine Mounts: The engine mounts themselves might be slightly different between the 1995 and 2001 versions of the 318. You might need to reuse mounts from the 1995 truck, or possibly source new ones depending on the condition of your existing mounts.

* Wiring Harness and Computer: The engine harness and PCM (Powertrain Control Module) are definitely not interchangeable. You absolutely *must* use the harness and PCM from the 1995 truck. The 2001 318 will have different sensors and wiring. Attempting to use the 2001 system will result in a non-functional truck.

* Exhaust Manifolds: These are *likely* interchangeable, but not guaranteed. The bolt patterns are probably the same, but you need to verify. A slight difference in the flange could cause issues.

In short: While the block and heads are likely compatible, you cannot simply drop in the 2001 engine and expect it to run. You'll need to swap over the essential parts (wiring harness, PCM, possibly mounts, and potentially manifolds) from the 1995 truck to the 2001 engine. It's a significant undertaking and not a simple swap. You'll be doing a lot more than just engine replacement.