Can I mate a T56 to an LM7 that was originally behind an automatic, and will the ECU complain?

Yes, a T56 bolts to an LM7 that came behind an automatic, but the ECU has to be reprogrammed for a manual. Our go-to is a Camaro tune, mainly so the reverse lockout works; the ECU activates reverse lockout below 5 MPH, and without it you can still muscle the shifter into reverse, but it isn't easy. You don't need the T56 transmission harness; making your own wiring for the reverse lights and reverse lockout works fine. We recommend wiring in the T56 VSS signal as well, since it helps the computer run the LS and makes tuning easier, though we've seen it done both with and without it.

Check this first:

• Have the ECU reprogrammed for a manual (Camaro tune)
• Wire the reverse lights and reverse lockout
• Decide whether to wire in the T56 VSS signal

Based on what we've seen work across our own builds, our friends' builds and the wider LS community, reviewed by our lead tuner (20 years of LS tuning). Every combination is different, so use at your own risk and check our safe tuning limits before any wide-open pass.