There is a bolt-on kit.
http://sikky.com/products/mount_kits/ls1__s14_240sx
It's on the high side but all you need is the wiring, ECU and exhaust
Other options are:
http://www.daftinnovations.com/
http://www.hinsonsupercars.com/s-3-n...0sx-89-94.aspx
It might cost more up front but remember you are getting 340 hp and getting 30 mpg.