Hi guys,
I need help to find an ECM for my brother's 1999 Ram 2500 Van.

I've seen many on the web that should be compatible with our model, even if the part number is not the same.
P/N of our ecm is P 56040 115AH
Most of them have a different last letter. Do you know what it means? What should I check to be sure they are ok for our van?

I read also that the reconditioned ones need the VIN for reprogramming. What is it? Maybe this is a stupid question but I'm italian we do not have any VIN :P

If you know good sites where to search any advice is welcome.
Thank you very much!