I don't think heavy duty timing would be necessary at that power level but if it's not much more $ then do it.
Coil packs - might as well then.
Radiator - getting the stock one refurbished may be a lot cheaper and will be like new. I'd Get a heater core from a wreck too, but that's just me. Replace your thermostat and radiator hoses while your at no matter which way you go.
I've heard of turbo failure doing this on RB26's only and even then it's so rare that people known for vast amounts of experience haven't seen it and think it's impossible. I heard - through these forums - of it twice, both on RB26.
I don't know enough about R33 brakes to advise you there. Try the Suspension and Braking forum on here.
Mmm, Nismo 1.5way would be nice. I want one. SAU NSW members get 10% off at GCG $1950 list price minus 10% = $1755. Up to you.