Hey mate.. Used to have 240z. You will love the car dude with an RB in it. Adelaide Z cars are doing RB conversion for customers Race 240z at the moment, and Vic Z club has a few members with RB's in their old school Zeds. As long as the 260Z was built pre emissions then you can get away with blue murder, but to be honest I would still run a cat. It will be less hassle when you get pulled over if you dont have to "explain". Another good conversion is SR20 in 240/260 as the motor sits further back giving slightly better balance. Get on a Zed forum quick mate.