I have a .064 4130 steel blank.  I know the ejector gets hardened, but which holes?

the trigger and hammer pin holes will need to be hardened as well

Quoted: the trigger and hammer pin holes will need to be hardened as well

Is that all, no trunnion holes?

hmmmm, you know i cant recall actually. you might want to check out the article on surplusrifle.com, theve got an article on building from a flat and heat treating is included in it.

I don't think the trunnion holes need to be heat treated. In fact I hope not. I didn't do mine. 500 rounds and no problems yet.

I don't think you'll want the trunion holes hardened as the swell head rivets need to push the reciever into the trunnion...If you harden them they will crack... My .02$
Just do the trigger holes (remember to temper immediately after) and maybe the grip hole....
Do not force the trigger pins!!!! I repeat do not force the trigger pins. Polish the holes till they fit.... If you heat and quench then try to tap the pins in you WILL crack your reciever!!!!
Ask me how I know
Depending on how your doing your build (mig tig rails vs. spot weld) I fit my pins first then drill my holes for the rails (I mig the rails, and they must be fresh clean metal to stick) weld the rails then heat and quench then temper....  Install the rails first or you'll have a hell of a time drilling the holes.... This worked for me