Should the squirters in my 850 Mighty Demon mechanical secondaries be changed in matching pairs? {same # primaries & secondaries} 73 Duster/440/4 speed. Thanks, Dave

They don't have to be. But they should be close. I like ot run my carbs with heavier primary squirters than the secondaries, but often heavier jetting in the secondary as well. It all depends on what your motor wants and needs.
I would start out with them being hte same. And then play with your jetting, and accelerator pump delivery, and get that close to where you need to be, and then play with the squirters to get the response just right.