Is it possible to get a RHD harness to fit a US fc or is it not worth the effort or just plain impossible?

 

It's possible but not worth the effort unless you really can't find a LHD harness.

 

Is it possible to use a usdm turbo II harness with a jdm 13bt? The site that I was thinking about using says that, "For most engines you cannot use the japanese wiring and you must use your existing wiring." How much modification would be required if any?

 

If you have a 1986 car like the site says you have, then do NOT use the Turbo EM harness on the engine. Use your non turbo harness. Just a few wire changes.

I say to NOT use the Turbo EM harness even though it can be made to work. But there are MORE wiring changes that you'd have to make doing it that way instead of using you non turbo harness on the turbo engine.

The Turbo EM harness has different pinouts on its two orange plugs (near that big black, round grommet) that connect with the Front harness. Plus the turbo EM harness carrys no alternator wires like the non turbo EM harness does.

There's a jpg of Some one elses EM harness I stole off the net. See the two ORANGE plugs? Those are the ones I referred to above. The pinouts on the turo vs non turo are different in these plugs. It's preferrable to use the non turbo EM harness.