I understand Barry. My question pertained to the grammar of the Greek specifically the phrase εἶναι ἡμᾶς, the infinitive followed by 1st person plural in the accusative (or any pronoun in the accusative, for that matter).
Well, it is good that you have narrowed down the question now.
The original post was so general that, as you can see, some were looking at the "immaculate." Others were looking at ἐν ἀγάπῃ. I myself were looking at a few other things like:
καθὼς should probably be translated as "just as" rather than "even" because here Paul is starting to list the spiritual blessings mentioned in v. 3, and that God's choosing of us is one of them.
ἐν αὐτῷ should probably be translated as "in Him" rather than "for Himself." The "self" is not there. Two persons might be in view here (see v. 3). God the Father (of our Lord Jesus Christ) blessed us with all spiritual blessings, just as He (God the Father) chose us in Him (our Lord Jesus Christ). Of course this is subject to interpretation but "in him" is at least more faithful to the text. If you translate "ἐν αὐτῷ" to "for Himself" you somewhat limit the possibility.
But as to question of εἶναι, in translation some theology is almost always there, and a decision has to be made. For straightforward translation, it could be "he chose us in him before the creation of the world to be
holy and blameless in his sight. (NIV)" Some might consider believers are holy and blameless (positionally) and such translation would be fine; but others might consider that we are certainly imperfect and not blameless, but God chose us so that we can become that. With such consideration, one would translate it as "he chose us in Him before the foundation of the world, that we should be
holy and blameless before Him (NAS)"
Note that although NAS is generally considered more wooden translation and NIV dynamic equivalent, in this case it seems to be the other way around.