Just make sure no one sells you RB26 pistons as RB30 twin cam pistons as many companys do.Use a piston made for the job like CP and Arias.
RB26 piston sits way down the bore and thats very dodgy.
We are building 30s now using CP pistons that are made for the job and their working very well.Ross is one piston thats sold as an RB30-26 piston that is really an RB26 piston and its a long way from the right piston for the job,5mm or so down the bore.
RB30 etc crank oil pump drive extensions are cheap in WA now, cheapest in the country and done very well.
Theres really not many down sides to RB30-25-25 engines these days as there well catered for now,I have had 2 gearboxes fail on the dyno in high output 30s but the OS cross mission gear set is lasting.