H53I

https://www.amayama.com/en/catalogs/lexus/ls400/1-sedan-left-xf10-1989-3470/transmission-and-chassis-2/front-steering-gear-link-133 That has a lotta part numbers n some diagrams, might help https://www.lexuspartsnow.com/parts/lexus-nut-castle~90171-12002.html?vin=&make=Lexus&model=LS400&year=1991&submodel=&extra1=&extra2=&filter= (d=USA)&location=power_train_chassis/front_steering_gear_link,,45046A Thats the outer tie rod nut. Maybe theyre the same, if not it might help finding the inner nut. Also I think I read that bolt is Left Hand Threaded.