For everything to go as planned, you need a few things that absolutely MUST work.

1.) A "known good" carb (and fuel pump)
2.) A "known good" ignition
3.) Stable and sufficent voltage, at least a good battery, if not a "known good" alternator and regulator as well.

Mixture has to be close enough to run for 20 minutes without overheating
Ignition must work and timing has to be quickly adjustable , also no overheating.

SO.

How do you KNOW if brand new untested carb and ignition parts will actually work ?

I don't think you can know that.

I have an OLD orange ignition box that worked 25 years ago. But I am thinking about firing the engine with a points distributor / coil, one that has been
checked on an old distributor machine and has a known advance curve. If the points gap is set, it should fire the engine, right ?

On the carb, if I put on a brand new Edelbrock/Carter and go through it first to make sure there is no debris in it, it should fire the engine, right ?

What else am I missing ?