Is it too difficult to swap the engine out of a '82 240D and replace it with an engine out of a '79 240D?

OR, could I put an '80 300D in my '82 240D? Just curious.

I found a '79 240D with 75,000 miles on a complete rebuild and I can get it cheap! Real cheap!

Ideally , you would want to convert it to manual trans when you have it all apart on the floor...