[ronaldk]

If you have good blue spark and fuel pumping in to tb like you say in op you even tried starter fluid. and now you verify timing is in spec I suspect improper air to fuel. A clogged cat that will not let eng breath will not allow fuel to ignite. When you have fuel,spark and proper timing you should have running eng if not unless you cooked all your valves or rings the only other thing is improper air to fuel. like map sensor but spraying ether it should have reacted. I can think of nothing more.good luck p/s if you confirm cat to be good do compression checkI do have one more thought, when you overheated eng you may have dropped a few liffers.I had a 305 van when I first started my busn a very long time ago any ways one push rod made a hole in rocker arm closing one valve on one cylinder and I could no longer drive it had no power maybe if more that one dropped it may not start. Long shot but if you take valve covers off someone can crank you can make sure all valves move.