on the build plate it should have 1 letter and 3 numbers.
you need the front diff out of a 4x4 hilux. the build plate i think only lists the rear if i remember correctly.. the code for the rear will be GXXX, first 2 numbers are the ratio code. check them against the list above and thats the ratio. front and rear ratios are the same.
toyota ring gears will have the ratio actually written on them.
sometimes its just the number of teeth. something like 41 11.
or just the actual ratio in a circle, like 4.8 with a circle around it. thing to note here is when its written like that, the figure has been rounded. eg my t series 4.778 has 4.8 written on it. but the code on the car was T362.