Truck wont start without starting fluid, but after i spray it itll run all day long.

[Swatson]

I have a 66 chevy c10, with an inline 250 motor from a 70's c10. When i try to start it cold itll just turn over and over again but won't start. I can spray starting fluid into the carb and it'll crank fine and after it warms up, it'll idle fine and I can drive it all day.
And after the engine is warm, I can turn it off and crank it again and it'll fire right up.
I've put new plugs and wires, new fuel pump(mechanical), new fuel lines from pump to carb, new fuel filter, I've rebuilt the carb which is a Rochester monojet and put a new fuel filter in the carb. Any help would be greatly appreciated. Thank you.