I have one.
Only if you want to make your car unique and get some niftly JDM only parts.
Yes but only a tiny bit. MK3 has good representation as well.
Just don't plan on reading a word of it. It is entirely in Japanese besides chassis codes and HP numbers. Still cool to look at though, and interesting to see some different parts.
Also remember MOST parts for the 70 will be designed for the 1J as far as engines go. But anything besides engine will work fine.