Will not stay running

I changed the ignition because the key would just turn with out turning the car on. After I did I found out it was not the ignition it was the ignition pin. So I put the old ignition back in and I changed the ignition pin. When I started it and started and ran fine for three seconds and the shut off. It did that three times and then would not do nothing. It locked the starter out for the anti theft system. I think it was because I had put the new ignition in and it did not recognize the key and when I put the old one in it tripped the security code. I towed it to two different garages to have the code cleared because that is what everyone on Google said it was. Both garage said it was the sender or the receiver of the security unit and they could not guarantee me which one it was for sure. One cost $1,300.00 and the other $1,100.00 to do. It would be a gamble to do just cross my fingers and hope we picked the right one first or we would have to do both basically it would cost me $2,500.00 to fix. I said no and brought it back home. My buddy told me if I could find one being parted out with the matching computer that I could change that and the security units and the key and put in mine and it would start up. Would that work? Does anyone have any solutions I should try? I found a 2005 would that work in my 2006 or does it have to be the same exact year? Thanks for your time.