I changed the odometer in my car when I did the swap.
I installed a USDM speedo into a JDM guage cluster and had to change the odometer to read the correct milage.
You have to disassemble the speedo and reset the dials. It’s pretty easy to do if you have a delicate touch.
It’s illegal to roll the milage back. You would be suprised at how easy it is to get caught now, due to new laws. If you go to the dealer or have any work done to your car at a glass or body shop they log your milage to the vin on computers / internet data base.
i know they keep track of it. i just had my indiglo burn out and when i put them in i broke my gas needle and temp gauge. i want to put in leds so i got a new gauge cluster to do this with. i was going to change my new cluster to match but it seems to hard. i took apart my old one this weekend and put it together, easy. but decided not to screw with the new one i just got.