RB20 galleries don't line up, (so i'm told) if you want to do a DOHC conversion, you need to use the 25 or 26 head.
All the information that you need on turbocharging an NA RB30 can be found here:
click me!
You will find a list of all the parts you need in there as well, and a couple of tutorials.
You can use the VLT computer, but it's not a straight swap, you have to wire the ecu so that the R31 fuel pump will work.
As far as all VLT parts being "rooted" you will find that all the ones that are still around have been looked after.
All the thrashed ones went to turbo heaven a long time ago