The heartbreak of engine swaps........
I would find out first what engine you have, then search for articles
telling what ECU you should have.
Once the correct ECU is in, search for what wiring harness is correct for the
ECU and the engine, bite the bullet and put it in. Toss the old harness
into a box to scrounge parts from later on. Dx/Ex/Lx doesn't always matter
unless they had different engines.

As a general rule, most people don't buy a car that doesn't run well.....
unless it's dirt cheap. Any swapped car should come with documentation
to tell you what you have........or be dirt cheap.

Or start fixing stuff that is not the engine, until everything else works, and then
make the engine work.-Bob