I've been throwing around the idea of switching to a gen iv 6.0 from the LQ4 that's currently in my Chevelle. After reading through a ton of write-ups it seems that integrating external inputs and outputs is a lot more difficult with the E38 and E67 systems than with the old gen iii stuff. From my reading so far, these appear to be the biggest challenges:

- Cruise control with discreet i/os for given functions. Legacy GM switched deliver +12v inputs for cruise on, resume/accel, and set/coast. The Trailblazer E67 operating system is the only one that can handle these.
- Electronic cooling fans. It looks like a patched Trailblazer OS is available to add these controls.
- T-56 VSS input. Platforms which were automatic-only would have had the VSS signal going into the TCM instead. I saw multiple posts about installing a VSS in the C3 66 and 67 pins, however no seemed able to confirm that it worked in their own swap. More specifically, does it apply to all operating systems (such as the Trailblazer OS).
- T-56 reverse lockout. This same issue would apply to automatic-only platforms. For my LQ4, I was able to email HPTuners customer service and have them manually add reverse lockout parameters and identify which pin would supply the switched ground. Is the same approach possible for the gen iv computers?
- Clutch switch input for cruise control cancel. Same issue as above.

These issues have been around from the start and based on my experience with adding the reverse lockout function to an 03-07 Silverado operating system, it seems like it would be possible for HPTuners or EFI Live to release a custom operating system that would include all of the necessary functions for a common engine swap using an E67 ECU. There would be two options:
1. Take the 07-08 Trailblazer OS and swap all of the necessary parameters for a manual transmission.
2. Use a CTS-V OS and add the ability to take discreet cruise control inputs. I think this would be preferable because you'd have an easier time adding a supercharger, but I don't know how realistic is to change the code in that manner.

Am I understanding these issues correctly, or is a simpler solution available? (short of switching to an aftermarket engine controller)