Your guess is as good as mine on what was behind the 5.3 ! This is a Frankenstein swap ! I have pieced everything together from Craigslist and ebay. I thought I did all the research and could use my pre `95 4L60 on the 5.3. I would just have to change the internal harness to that of a `96 and later. All the trans controls are from factory on the pcm I would assume. I just told Brendan from lt1swap.com to remove vats and give me some better fuel mileage. Will check the wires on the vss but I soldered them to each corresponding wire and from the harness by color.