i think you might have to take it to a shop, i had custom wiring done on my 00 gts, no one makes harnesses for the celica's, thats what ive heard.
2000 GT-S - SOLD, 12/2003
1986 AE86 GT-S - STOLEN, unrecovered, 2/2004
1985 AE86 GT-S - built 4AGTE, SOLD 10/2009
2004 Camry LE, SOLD, 5/2007-10/2007
1994 GS300, 2JZGTE, HKS T04Z, 10/07-Current