One of my many hobbies includes electronics, so I'm the go-to in our group for PCM hacking and such. I don't call myself a tuner, because I'm not.
There's some pretty powerful tools out there since LS swaps are so popular. Doubly so for the Gen III SBC, since there's no DOD nonsense and they can be had in drive by wire or drive by cable.
From what I understand, a lot of this can be done on a phone. I don't mess with that. It is much easier and less risky to use a laptop. It does not need to be powerful. I'm using a Dell 5414 for all my various car needs, and it has a 6th gen Intel processor. That's about 9 generations back at this point. Other than a computer, you will need:
An OBDX Pro VX dongle: https://obdxpro.com/product/obdx-pro-vx-obd2-diagnostics-and-tuning/
PcmHammer: https://github.com/PcmHammer/PcmHammer/#installation
Universal Patcher: https://universalpatcher.net
Key on, engine off, plug the dongle into your computer and then your car. Follow PcmHammer's directions for downloading your BIN file from the PCM.
Once you have your BIN file saved, MAKE A COPY! DO NOT MODIFY YOUR ORIGINAL. Put your original in a safe space on your computer and rename your copy so you know which one to modify. Open Universal Patcher, and click the "Tuner" button. Go to File -> Open and select your BIN file. You are now at the point you can modify your BIN or "Tune".
Universal Patcher has a section specifically on how to disable DTCs here: https://universalpatcher.net/dtc-disable-example/
Toolshed Adventures has a pretty good video on how to change your speedometer readout for tire size and gear ratio. Link starts at 7:45 where he gets to it:
You can also use Universal Patcher to tell the vehicle what gears it has, but if you recalibrate the speedometer value, you don't actually need to do that.
After you make your changes, save your file. You can then use PcmHammer to write the BIN back to the ECU. Again, follow the directions there.

I built myself a little bench harness with scrapyard parts so I could do all of this out of the vehicle in the comfort of my own home.

There's lots of stuff out there on how to build your own harness, so I won't get into it unless someone needs help.
It is pretty simple, but if you're worried about it, you can always go to the junkyard or eBay and pick up a spare PCM.
I do this stuff for fun, so if you have any questions, just ask!
There's some pretty powerful tools out there since LS swaps are so popular. Doubly so for the Gen III SBC, since there's no DOD nonsense and they can be had in drive by wire or drive by cable.
From what I understand, a lot of this can be done on a phone. I don't mess with that. It is much easier and less risky to use a laptop. It does not need to be powerful. I'm using a Dell 5414 for all my various car needs, and it has a 6th gen Intel processor. That's about 9 generations back at this point. Other than a computer, you will need:
An OBDX Pro VX dongle: https://obdxpro.com/product/obdx-pro-vx-obd2-diagnostics-and-tuning/
PcmHammer: https://github.com/PcmHammer/PcmHammer/#installation
Universal Patcher: https://universalpatcher.net
Key on, engine off, plug the dongle into your computer and then your car. Follow PcmHammer's directions for downloading your BIN file from the PCM.
Once you have your BIN file saved, MAKE A COPY! DO NOT MODIFY YOUR ORIGINAL. Put your original in a safe space on your computer and rename your copy so you know which one to modify. Open Universal Patcher, and click the "Tuner" button. Go to File -> Open and select your BIN file. You are now at the point you can modify your BIN or "Tune".
Universal Patcher has a section specifically on how to disable DTCs here: https://universalpatcher.net/dtc-disable-example/
Toolshed Adventures has a pretty good video on how to change your speedometer readout for tire size and gear ratio. Link starts at 7:45 where he gets to it:
You can also use Universal Patcher to tell the vehicle what gears it has, but if you recalibrate the speedometer value, you don't actually need to do that.
After you make your changes, save your file. You can then use PcmHammer to write the BIN back to the ECU. Again, follow the directions there.

I built myself a little bench harness with scrapyard parts so I could do all of this out of the vehicle in the comfort of my own home.

There's lots of stuff out there on how to build your own harness, so I won't get into it unless someone needs help.
It is pretty simple, but if you're worried about it, you can always go to the junkyard or eBay and pick up a spare PCM.
I do this stuff for fun, so if you have any questions, just ask!
