AT180 = 4A-FE engine = 1.6 L
ST182 = 3S-GE engine = 2.0 L. with 170 PS.
ST183 = 3S-FE engine= 2.0 L. with 140 PS. or 3S-GE,4 wheel steering, Japanese market only
ST184 = 5S-FE engine = 2.2 L., US and Astralia
ST185 = 3S-GTE engine = 2.0 L., turbo + 4WD
AT200: 2ws, 7A-FE = 1.8 L. Export (ST), UK (ST, SR).
ST202: 2ws, 3S-FE or 3S-GE. Jap (SS-I, SS-II, SS-III),
export (GT, Convertible).
ST203: 4 wheel steering, 3S-FE. Jap market only (SS-I).
ST204: 2ws, 5S-FE. US (GT, GT Convertible), Canada
(GT, GT-S), Aussie (SX, ZR), NZ (GS),
other export (GT, GT Convertible).
ST205: 4wd, 3S-GTE. GT-Four, GT-Four WRC.
I got that from here
http://www.celica.dds.nl/en/celihist.htm
I didn't really see much on the ST16X series