IF Galil receivers ever become available, could I take a Galil milled
receiver, mate it to a Bulgarian 5.56mm AK kit, and set it up to use Galil
mags?

IMO, its more trouble than it's worth... For a little more than you will end up spending, you can simply build a Galil.

Quoted: yup. why run galil mags? bulgarian .223 mags are inexspensive, durable, reliable and available by the railroad car. ohio rapid fire will gladly take your money for their authentic galil receiver. to me, that merits building it up with a set of galil parts, though.

Camp,

I'm going to build several Galils.  I've already got one parts kit and plan to get more.

But what on earth does that have to do with anything? I'm curious.

Quoted: why run galil mags? bulgarian .223 mags are inexspensive, durable, reliable and available by the railroad car. .

And this answers what part of my question?

First of all,  I don't trust the Bulgarian 5.56mm mags.  I have about a half dozen of them and I just don't see them as all that reliable.  At least not long term.

Secondly, if I'm getting a Galil and a bunch mags then I don't really want to buy an additional bunch of cheap plastic Bulgarian mags.

Third, I have no idea what an M1A1 is.

If it's radically expensive then I just want bother with a 5.56mm AK and I'll stick with Galils, which seem to be better rifles anyway.  My original goal had been to get several Galils, and then have an AK which used the same mags (for aesthetic purposes).  However, if it's going to cost a lot then I just won't bother.   I'm getting a bit tired of AK's anyway.