Unless you have invested a lot in the body, I don't think it's worth it. Could be better to get a vehicle already with the 4M40, unless that gets too expensive, or unless you get the engine for free as you say and you like tinkering <img src="/forums/images/graemlins/kewl.gif" alt="" />

You get 125hp and 292Nm vs 100hp and 245Nm in the 4D56, both with turbo and intercooler.

I've heard the 4M40 is a little less fuel hungry than the 4D56.

4M40s have an ECU, probably the earlier ones didn't.

The good thing is that if you also get the transmission, you'll upgrade to SuperSlect.