if its a track car, i'd do stock housings with koni 8611-1257 inserts. however this requires fabrication work and maybe more than u want to do, but i can't stress how important good suspension is over outright power, but again thats personal preference. i gave up a new gtx2863r turbo in place for a custom double adjustable suspension
the biggest issue with bc racing coils is there's actually bout an inch or less of travel before it hits the overly stiff bumpstop
u can try replacing the bushing with a progressive koni, but the stiff ride is the non digressive damping , bump stops, less so than the spring itself. over most bumps the car is fine on 7kg/6kg, its anything over an inch in size and hit the bumpstops which is the backbreaker
i personally like the nismo rear diff and i dont mind it all on the street, but thats subjective and everyone's tolerance for nvh is different
u can hear the clunking in a couple of my videos, its noisy at first but i barely notice it anymore as i've gotten used to it
it sees track use regularly and without the diff, the car understeered so much i contemplated selling it. mind u, im used to driving miatas, s2000's. i want the front end of the car to do something specific, and the pulsar just can't. the nismo rear diff has helped a fair amount by inducing rotation and allowing me to put power down, previously as soon as i lifted the inside rear, i couldnt get any power down. its possible my rear viscous was dead.