Lets say you switched an engine from a '95 Caprice to a '94 Caprice. Would the milage reading from the '95 engine be shown on the '94 (electronic dash)or would the '94 still show the miles of its old engine?

Lets say you switched an engine from a '95 Caprice to a '94 Caprice. Would the milage reading from the '95 engine be shown on the '94 (electronic dash)or would the '94 still show the miles of its old engine?

Since that information is contained within the PCM, I'd say it'd show the original info to your car.

Not correct, the mileage is stored in the speedometer. In fact the chip can be changed when they are repaired, BTW then the speedo reads 00000 as if it was new.