I have a 1981 Honda Civic and could possibly get a built D series motor and trans, not sure exactly what kind yet and lots of other parts for free. How hard would this be to swap into my civic, the transmission and carb are bad so I wanted to just swap in a new motor.

 

It's actually not all that bad. I have a neighbor who is good with motors and can weld, and he said the most difficult parts would be welding/fitting the exhaust into the bay and relocating the motor mounts. If you have someone handy with welding and engines, it can be done. The new ECU has to be carried over as well. I have a 1983 that I am currently looking into putting a B18B in. My motor is shot.