you can order either from your local hobby shop, and they are also commonly available from Tower.
Both are Q-500 aircraft...... ARF construction. Good airplanes.
As Dave noted, Jett .50..... and 150 is in your grasp. And guess what..... you get to have wheels too
if you want to go for the top speed, get the SS muffler combined with the Jett 50. Tuned for higher rpm... perfect with the pylon D-1 series APC props. Runs like a 428 pylon engine on steroids.
If you want something more along the lines of a Magnum, look up [link=http://www.rcuniverse.com/forum/showprofile.asp?memID=92292]Angel [/link] on here (past threads). He has a few aircraft that will most definately suit your speed needs.
Bob