Hey according to a lil research, HKS dumps for 32/33/34 gtrs are the same and the 34vspec 1 will fit too. The only difference is that the 34vspec one has an extra slot there the O2 sensor goes (something along those lines, from HKS dealer) which you can seal off using an O2 sensor bung (easily obtainable from any exhaust shop).
Since you're doing the turbos I would recommend doing the dumps as well (pain to change just dump). Remember I bought those HKS Dumps sometime ago (I found you'll need to take turbos off etc to fit them), I'm selling them now if you're keen. PM me if you're interested.
Fitted the HKS front pipe over the weekend and somehow it does feel smoother. I would love to put the dumps on but could justify paying 4hours+ labour just for that (but then again if you're doing turbos, its another case).