A simple search on this site will show you a number of ways to make a gasser. There is a dedicated forum too. http://www.rcuniverse.com/forum/forumid_92/tt.htm
I'm sure all the conversion guys would laugh at the comments made here.
You can go as cheap as the weedeater in your garage,(or $59 bucks on sale at depot) or buy a big bucks custom job.
If you want to create a monster that you can be proud of, there is a vast amount of knowledge on this site.
Good luck and have fun.