How do you tell if it is a GTX by looking at only the VIN number ?

There are 17 numbers in the (USA) VIN numbers.

Example: JM1 BF 23 4 7 J 0 100001

The first three are the World Manufacturer Identifier.

JM1 is for Mazda's US and Canadian cars.

4th and 5th characters are the car line series.

BF is for the 323 (in 88-89)

6th and 7th are is the body style code.

22 is 4 door

23 is 3 door hatch back

34 is hatch back

8th is the money code number

2 is 1600cc EFI 2WD

3 is 16oocc DOHC Turbo 2WD

4 is 16oocc DOHC Turbo 4WD

The ninth digit is a check number from a mathematical formula.

Keeps you from making up your own number.

10th digit is the year code.

J is 1988

K is for 1989

11th digit is the assembly plant

0 is Hiroshima

12th thru 17th is the production serial number

You want the 8th digit to be a "4" for a GTX