If you wanna swap something get a 240.

If you wanna learn more about the rotary go here:
http://auto.howstuffworks.com/rotary-engine.htm

Then here:
http://www.rx7uknet.dircon.co.uk/history.html
and here:
http://www.aaroncake.net/RX-7/why.htm

Then, after you get some history under your belt, go here:
http://www.rx7club.com

paying special attention to the archives and FAQ's

If, after doing some research you decide to delve into the world of the rotary, and have a prospective vehicle in mind, the following site will help you weed out the good ones from the bad:
http://www.fc3spro.com/TECH/h2b.html