if u r realy keen on doing the conversion there are a few things u gota consider first. its all good and well having a turbo motor but is the rest of the car up to handle the power difference. is it auto or manual? a standard na auto gearbox will not hold the power of a turbo rb30 for very long even on standard boost. and the na manual is not much better. vl turbos came with a disk brake rear as apposed to drum on most other models excludin all calais, v8's and some belinas. the front brakes on the turbo model have a bigger booster bigger diameter disk and larger caliper and it does make a big difference. as u may have noticed non turbo brakes dont stop real well.
most turbo models also come out lsd. open centre diffs arent real fun in turbo cars. the gearboxes are also different heaps stronger.
if u are really serious about doin the turbo conversion the best way would be to keep ur eyes open for a damaged turbo vl and do the conversion urself. u can find them pretty cheap only bout 3 grand for a manual. but itlll save u money in the long run. its as time consuming job but in the long run u will end up with a much more reliable car with a near unbreakabe driveline.