Yeah so my question is what kind of bulbs do our ls400s use ??? Can i use H7 bulbs??? Im asking cause i found a good deal on a hid kit but its off of a mr2 and i wasnt sure if i could hook it up to the ls400 help me out you guys thanks

Your 91 uses a 9004 headlight bulb. In 1993 they started using a 9003 bulb.

In a word,,NO. Different bulb size will not match up at all. Post above ^ is correct for standard bulb size.