Advice Needed - Can't Start Rebuilt 273

Sick, I would check your valve timing. With low compression and the fact that you rebuilt the engine and it hasn`t run yet sort of points to an issue with the valve timing. You`ve checked the valve adjustment, firing order, and if you have spark and fuel then it`s got to be your timing and/or a lack of compression that`s keeping the engine from starting. All you need is a 1/4 spacer (I use stacked feeler gauges) and a dial indicator. It simply involves preloading your number one intake lifter (in essence making it a solid lifter) and dialing in your crank damper mark within ten degrees of the "O" timing mark. Check your fsm for the details.