Need answers to what Vtex said, especially concerning it running while you've had it.
Oil level and condition fine? Supply of gasoline not really old?
Is the timing set correctly, or is it slipped by a few teeth? That can be a culprit.
Also one thing I do when a car has been sitting for a long time and I'm trying to start it, is attach jumpers+another running car to the normal battery for extra juice, or put a battery charger on it set to "start" mode for extra juice.
I've even squirted some starting fluid into the TB before to see if I get a couple of burbles from an old engine.
One time I had a swapped in a motor that had been sitting for years, it wouldn't start even though we had timing, fuel, spark, and air. We were dumbfounded. Turns out we just had to keep trying to start it and eventually it came back to life.
After all these things you'll try, the ECU could obviously be the issue. But address that last.