Good luck with your first Zed mate , I owned a 260z for many years before getting married and downsizing to the Corona. I spent a lot of cash fixing rust and previous dodgy bog jobs from others. I can only echo what others have said - get it done right once. these old girls are super rust prone and it could end up being very serious.
Apart from that they are mean cars , I stuck with an L26 with a little bit of work and it sounded cool and still went ok. Dropping an injected engine into an old car is more work than others will lead you to think. "drops in there" isn't quite it. Remember bigger engine = bigger brakes and handling upgrades.
I got a lot of my bits of Ebay and from Motorsport Auto in the U S and A , many Z cars went to the US and they were the car that really sparked the import tuning explosion there.
I ran tokico shocks with lowered springs and a full bush kit , helped the handling like night and day.