rear end gear ratio

Anyone know how to tell what gear ratio an astro van has? Ones an 87 and the other is a 91. I believe the 91 has a towing package on it, not to sure though. Both are 4.3 passenger vans. Any help.

The 1991 vin is 1GNDM15ZXMBxxxxxx.
And the 1987 is 1GNDM15Z5HBxxxxxx.

As a security precaution, complete VINs should never be posted in a public forum. The last six digits are generally of no significance to the equipment except in a recall campaign, but the complete number can be used to find owner registration information, including the owner's driver license number, address, and other particulars. With that information, more about the owner can be learned than the owner may have intended.

As for your specific question, the information is not encoded within the VIN, but should be included on the RPO/SPID tag on the vehicle. The part number stamped on the front of the right side axle tube is also a good way to find out.