Do new aftermarket ignition switches work?

You should NOT waste time critically testing these with an ohmeter, for a few reasons. Check them under LOAD and for voltage drop across the contacts. Wiggle the key to check for intermittent contact

I would "rig" about a 10A load, and please don't ask where to get such a thing easy or cheap. If you have a nearby friendly junk yard, get some old headlights and parallel them up.