I have afterwards purchased Martelius muffler and 4.0kg/mm springs for front.
Those springs indeed made world of difference to way my car behaves. Theres still minor body roll, most of it due to yielding winter tires. Ride is still comfy. I'm thinking 6.0-8.0kg/mm front springs for next summer.
Quad throttle bodies are almost finished aside from intake plenum and injector positions because I dont yet have injectors. Otherwise I have most of the EFI gear accumulated.
I have also purchased HiLux calipers and Subaru calipers for rear. Those Subaru calipers were from front of one of those butt-ugly Coupe Leones. Original Subaru disk is 18mm thick and 242 diameter. Furthermore favourable features are big pad area, lots of clamping for hand brake(I have tested these calipers in my friends 555), inexpensive and I can use slim rotors due to decent looking desing(not very bulky). I hope these calipers are usable. Both rotors (front and rear) are still question mark to me. Pug rotors might be NO because one half-acquainted has RS-50 hubs that I'm thinking to buy but those are drum hubs. So rotor off-set might be out . Nothing more worth mentioning, I think...