Introduction

Hi all a newby here with a drug dealer black 09 freelander SE. I've had in the past a SIII SWB a SIII J.Craddock 12 seater station wagon a freelander 1 a disco and now a freelander 2. Here's my problem. The am on the radio doesn't work and I've had it checked to reveal I need to replace the unit. Now on the internet there are a few identical units but with different serial numbers on them and I've been told i must replace with the same serial numbers. Can someone explain why, surely if the units are identical and have the same sockets and fixings what do these numbers mean. Soz for the long moan but I want am to listen to sport.