Advice Needed - Can't Start Rebuilt 273

I noticed the 70#-90# of compression in all cylinders. You should have 150# I would say. It should run with low compression but have no power. If you haven't done it yet you should adjust the valves properly. If that doesn't cure it you may have to check the valve timing. Did you say that you checked the spark at the plug? It should be blue/white colored and not yellow/orange. My brother-in-law had a 65 Riviera with a no start condition. I came over and checked it out and the spark was orange colored and very lazy. It had a bad coil. He replaced it and it started and ran like a champ. toolman