Two Version of Rails on one machine

Hi,

I installed rails3 on my mac and after installing 2.3.5 using gem install rails -v 2.3.5, if I run gem list rails, I got *** LOCAL GEMS ***

rails (3.0.0.beta, 2.3.5)

But if I run rails _3.0.0.beta_ test got the following error can't find executable rails for rails-3.0.0.beta (Gem::Exception)   from /usr/local/bin/rails:19:in `<main>'

How can I create rails3 project?

Thanks