Help Finding Matching Numbers 1982 GT

I have a 1982 GT. I pulled the engine and transmission out. How can I tell if they are original to the car. The car still has the 7.5 rear in it. How can I tell if that is the original rear as well?
Where would the numbers be located on the parts? How do you decode them to find out if that is the original equipment?
The 82 still has the 2 barrel Holly on it. Would I be able to tell if the Holly and the manifold are original?
If this equipment is original I will keep the equipment in storage in the garage. If not I will get rid of it. For those of you that are married, I'm sure you understand about picking the battles with the wife.
I also have an 85. Would the numbers be in the same place? Is it the same decoding method to tell if it is the original powertrain?
Thank you all in advance for your help with this,
Joe
:SNSign:

Thanks for your help.
If the car was equiped with the engine I will keep it. Not so much for the value, but for the cars history. When I was growing up in the late 70's and early 80's the performance cars were all show and no go. Then came the 82 GT. With only 157 hp, that car started the horsepower wars again. Mustangs have to be one of the most abused cars in history. They only came with 1 engine. Why not keep the engine on the side? Not really worth anything to anyone.
Who am I to break u the car and engine that started it all.
Thanks again for your help