alright lets say my car has 70K miles on it, but i plan on swapping a V8 into it that has just 10K on it and i have to swap the PCM and everything, wont 10K show up on the odometer now or do they go back in a reprogram the PCM to make it read 70K? Just something i was thinking about the other day b/c im about to do a LS1 swap.

 

The cluster should show the mileage of the car not the engine.

Just a thought... I would suggest that it would be cheaper to simply Buy an LS1 powered car using your current ride as a trade in then it would be to swap motors. I have a friend that did the LT1 swap into his 94 Firebird and there is a TONof work. He did the full conversion, Motor, Six Speed, Rear End, Brakes, Console, Dash, etc... etc...

You will be nickel and dimed as you have to get all the little stuff and getting it all to work isn't sometimes exactly plug and play

 

The miles are stored in the cluster itself. You can swap out cluster to reflect the miles on the new motor. I did an LT1 swap for $2500 total. That included buying a wrecked z28, same year as my car wth 20k miles on it. Paying a shop to do the swap for me, and them doing extra things like installing lt headers, 3:73 gears in the new rear, high stall TC, and some other odds and ends.