I have a 1984 b2000 that turns over, but won't spark to go into idle. So far in rebuilding it we've replaced the
Battery
Alternator
Spark plugs & wires
Distributer
Ignition coil
Starter
Fuel pump
Carburetor
Fuel filter
Air filter
Manifold hoses
Radiator hoses and cap
Fuses
And a bit more I'm leaving out either for lack of relevancy or just general forgetfulness.
Do y'all have any thoughts on where I've missed something to let it keep giving me trouble? Thanks in advance.

 

You could run a 12v wire to the coil from the battery so that you know the coil is energized when the ignition switch is in the START position.......just to eliminate that possibility. Some of the Mazda ignition switches have issues related to that. Welcome to the forum.

 

Spray some aerosol starting fluid into the air cleaner or carburetor body, try to start, do this a few times. If it runs for a few seconds then quits out, you have a fuel delivery issue, start there. If it won't run at all when you do this, then it's a spark issue, work on that. This is a common first test to help isolate the problem when the engine spins/cranks. And remember: just because the engine can crank fine, doesn't mean that the electrical part of the ignition switch (the "run" circuit) is OK.