You could put a 6.7L HSV motor into a 86 if you really want. It just has to be done properly and signed off by an engineer.
What ever your project is, there is a process to do it right.
Step One, after you've got your ideas together, will be to go see an engineer or 3, to see what they will and wont do. Safe Vs Not safe.
If you do step one, you will save a lot of time and money.