It's the same transmission, keep in mind the 4.3 is still old style SBC instead of LSX, so the NV3500 in my '06 will be the same as the one in your '89. Physically anyway there may or may not be differences in ratios and what not. I know S10's got different ratios, and the NV3500's Dodge used seem to be holding a lot more power (I'm still looking into whether or not there interchangeable with a simple bellhousing swap)