also the new renesis engine in the rx8 also doesn't have as many of the reliability problems that plagued the older rx7 rotaries
one a side note, if you're not totally set on the smart roadster, you may want to look into the Attack by K1 Styling. it's an easy to assemble kit car and it has a really big engine bay and is inexpensive. since this is a project with your buddies, it may be fun to build the car completely from the ground up.
http://www.k1-styling.sk/