It shouldn't be a problem. You MAY have a very slight camber issue, but with the Pro Springs, it won't be enough to justify a camber kit. I wouldn't recommend going much lower than what the Pro line gives you. I have Sportlines and the drop forced me to mod my rear suspension.
FYI, one of the installs on
http://www.240sx.org shows how to correct rear camber with simple modifications. If it ends up being a problem, check that out before you buy a kit.
Good luck!