The threshold question, as Stan notes, is how much rust does the car have. The universe of people who can properly do metal work on these cars is pretty small, so rusty cars are much more expensive to restore.
If the car is not worth restoring, be advised that it takes a great deal of time and effort to part out one of these cars. Markos has done a detailed thread on the process here:
https://e9coupe.com/forum/threads/deconstruction-thread-how-to-part-out-an-e9.21251/post-154944
The engine and drive train are not all that valuable, but in this case, you could pull together all the "manual transmission" swap parts and sell them as a package. See here for the parts you would need to pull and group together:
https://bringatrailer.com/listing/bmw-e3-e9-transmission/ (Note you should not expect to get anywhere near Paul's number, not only because four speeds are less valuable, but also because Paul gathered a bunch of new parts and because Paul has a good reputation, which buyers could rely upon regarding the completeness of the package.)
There are a multitude of small parts that are worth money, but you need to disassemble, describe, photograph, determine a price, answer questions, negotiate, collect payment, box and ship for each one. And if you are not a BMW person, you need to learn enough about the parts to know which ones are valuable and how to describe them. I suspect you can make about 50% more selling parts, but that doesn't take into account the hours and hours of time you need to put into it.
