I found 2 items relating to odometer law in PA.
http://www.dot.state.pa.us/public/dvspu ... ometer.pdf talks about how to legally deal with discrepancies between the odometer reading and the actual vehicle mileage. Seems to be mostly about how to properly document the difference when selling a car. In there there is a statement:
It is illegal to tamper with an odometer; sell, use or advertise any device for tampering; or operate a vehicle with a disconnected or non-functional odometer with intent to defraud.
(I added the bold/underline)
I take that to mean its not illegal, unless you are deliberately trying to commit fraud, which I don't think you are. It also does not say anything about having to use some certified shop to do the odometer change
https://www.pacode.com/secure/data/067/ ... 75.80.html is the PA inspection procedure, and the only place it mentions the odometer is at the bottom, the second to last item above "Authority" where it says to reject the vehicle if
" (6) The odometer does not operate, except on a motor vehicle at least 25 years old."
There is no inspection criteria about the odometer reading not accurately reflecting the true vehicle mileage.
So, that means that if you get the odo reset to some lower number, when you sell the car, you have to disclose the odo change but as long as its working, regardless of what the number is, it should not fail for the odo.
I swapped the cluster in my 1st 03 with a cluster from an 04, and set the new cluster odo to match actual car mileage. When I replaced that car with another 03, I moved the cluster to it and set the mileage to match the 2nd car. I was able to change the making an adapter and an IC clip, never had to replace or remove the EEPROM on the back of the cluster, just pull the cluster, take the back off, hook up the clip/adapter and run some odd russian software on a PC with a parallel port (hard to find on a computer these days)
I never found any mention of changing the mileage in the BCM. I'm actually not sure what a BCM is. Our cars have a main computer, sometimes called engine control module (ECM), engine control unit (ECU), powertrain control module (PCM) I know if gets the speedometer signal because my scangauge can track miles per gallon, but I don't know if it records overall vehicle mileage. I know that if it does, it doesn't have anything to do with what the odometer displays. The car also has a different thing called an integration relay or a multifunction module, used in door locks/keyless entry, and maybe a few other things, that's more in line with what I'd expect to be a body control module (BCM), but its got nothing to do with mileage and the odometer. So if a shop is telling you they might need to work on a fickle BCM, they probably are looking for your to provide them some free money.
So verify the laws in your state, and shop around for someone who will do it for a good price.