can a fc 13b N/A engine and transmission be swapped with a 13b turbo and transmission with no issues? like would I need a whole new wiring harness for the engine. Because I'm thinking of doing an engine swap on a fc rx7 it has a bad engine and was thinking of changing it to a turbo 13b, the engine comes with a transmission, would the old harness for the trans and engine work or would I need the harness and ECU for the turbo version. ( also would I need other stuff such as a driveshaft etc.?)

 

I just did this swap. Luckily I had a full T2 donor car. Yes you will need to modify or get a new engine harness, drive shaft, fuel pump, diff, ECU, exhaust. That's all I can think of off top of my head, but there are other post with this exact topic covered in detail. Use the search function to find them.
Good luck.

 

the engine harnii are different, but you can make the NA harness fit the turbo car. the S4 is more work than the S5

drive shaft and diff are also different, but you can buy a driveshaft that uses the T2 trans and NA diff, at stock-ish power it does ok. or you could even use the NA transmission (+ NA drive shaft and diff) for a while too.
this swap can be pretty big, and IMO its perfectly acceptable to break it into smaller chunks, like only do the engine this year, do the trans/driveshaft/diff next year

 

I would be remiss not to point out that this information is covered in the FAQ, with multiple links to writeups.