Just buy the damn car. If you're planning on doing a swap anyways, it's not going to kill you to wait to change the tranny at the same time you put a new motor in. It's also cheaper.

Auto to manual conversions on 240s aren't difficult, and there are tons of writeups. Don't listen to Hatch Man because he obviously has never dealt with 240's before.

http://www.240sx.org/links/installs/s14_5speed_swap.htm

It's basically this: take out auto tranny related stuff. install manual tranny related stuff. woohoo.