Does anyone know diff ratio of this car

I am not sure if they just stuck to one ratio for the whole run (doubt it). Look for the Service Parts Identification label, it'* a sticker that is likely in the glovebox or on the spare tire cover. It contains a series of alpha numeric 3 digit codes, known as RPO'*.

Cross reference the codes against this site:
RPO Codes.com- GM option codes,GM rpo codes,General Motors options

One of the codes should indicate the factory equipped final drive ratio

Just the ratio for the final drive I don't have the car I'm fitting the engine, transmission to a rally car just want to know wat ratio diff to use

divide the number of teeth on the ring gear by the number of teeth on the pinion and that will give the ratio. Example 41 ring gear teeth divided by 12 pinion gear teeth = 3.41666666666 or a 3.42 to 1 ratio.

If you can, get a picture of the data tag off the trans.