Can you convert your 86 back too the original state?

[Ivan141]

The only real modification you need to make from Levin to Trueno are the headlight brackets.
Those are spot welded on, and you need to drill them off to fit Trueno lights.
If you want to be able to swap back to Levin (sounds like a good idea), then I would just drill all the way through the spotwelds and put some rivnuts in place.
That way you can bolt the brackets back on later.