Is there a difference between ac and non 1996 blazer blower motor?

Yes, there's a difference between the blower motors for a 1996 Chevrolet Blazer, depending on whether it has air conditioning (AC) or not. The AC equipped version will have a more powerful blower motor to handle the additional air volume needed for the AC system. They are not interchangeable. The motor itself might look similar, but the internal components and possibly the mounting points might be different. Using the wrong motor will result in either a non-functional blower or damage to the system. Always use the correct part number for your specific vehicle's AC configuration.