The M7 (Size 1156) is correct for the 2000-UP Toyota Celica turn signal... I know this sounds crazy, but all 1156 bulbs, wherever you buy them from, are the same shape - they need to be modified for installation into the 2000-up celica.
Here are three links to different discussions concerning the 1156 Turn Signal bulbs.
http://www.ecelica.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=000424http://www.ecelica.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=000717http://www.ecelica.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=001373Install is simple, just choose what connector on the bulb that you do not want, and use a nail clipper to clip that "nub" off (or using a cement wall or curb to rub it off also works well). Your bulbs will then fit correctly
This is the same technique that everyone uses to install aftermarket 1156/M7 bulbs.