My 2c
finding rims in 4 stud is a b***h, stick with the 1's u have and save for a turbo r32, r33, r34, thats what i'm doing =D.
If you really want to have the 'skyline' garnish lit up have a look in the DIY section there are a few walkthroughs on how to make on yourself using S1 garnish, LED's and some paint.
Also WTF 6" tip, mine has a 3inch tip and thats pushing it for a NA.
As for mods possibly look for some coilovers, as nothing u do is going to do much for power, so you might as well try and make it quicker through the corners. I'll have to agree with reducing weight tho, first thing i would do is get rid of HICAS, should save about 30-40kg.
Good job getting rid of the tail lights tho they look crap.
*end rant*