Finally had a chance to test drive after my 4l80e swap. Worked as I had planned. All gears work including OD. This was on a 95 TBI computer with a 7427 computer. Seems Like it may shift a bit early for my taste but that is probably due to my chip coming from a service box van and I have not adjusted the tps yet. The big round plug do as a bunch of guides say to do. Easy to find the info on. Its the same even on the newer style computer that in 96 and newer. The tricky part to find is info on what to do about a ISS and where to pin it on the 95 TBI computer. Once you figure out how the letter/number locations work on the ecu plugs its not tricky just scary looking at that many wires. After you do the round plug end you will have 2 free wires. Of course those 2 free wires are white and tan/black. On the computer end for TBI those are pin E2 and E10. E2 is the white wire will be moved to F2. E10 is the tan/black wire will be moved to F3. Then you will need to go back to the transmission end of the harness and put on a ISS plug. F2 which is now the white wire form the round plug is now the positive for the ISS. F3 which is has become the tan/black wire is now the negative ISS. I can not find in my records which side of the ISS plug is positive and negative. I also did a 454/carb/HEI swap at the same time. I assume if you keep the stock engine and injection/distributor the computer would already be set up with the tach signal. But how I had to do it for a tach signal was hook a wire from the tach location on the HEI cap to the purple/white wire that is on the flat 4 wire plug for the stock distributor. This also has the added benefit of tripping the fuel pump to continue to run. For distributor power I just used the pink wire that originally powered the stock ignition coil. Of course you will need the correct chip in your ecu to run it. My transmission came from a 96 2wd suburban which is a completely different type of computer.