and
No clue on the 422 kit. I don't think gsxr400racer is selling them here anymore.
You can get a chrome ringed bucket headlight lots of places. Lots of bikes used them (other naked bandits, sv's, hornets...). The trick will be finding brackets to go around the USD forks. I think
Holeshot has them.
Belly pan and the solo cowl will be tough. I don't know that anyone makes them anymore. I'm not sure where you are but your best bet may be finding them in Europe where there are more B4s on the road. Wild Hair Accessories here in the US used to carry the cowl but I doubt they do anymore and it was pretty spendy.
You can fit a 160 rear but most recommend against it because it will negatively impact handling. Search around there are LOTS of posts here about that....
Good luck!