OT saved are indeed part of the NT saved, for we are now all one in Christ, part of the Spiritual Israel, but how we view the New Covenant is different, as I see it not as so much a carry over continuity, but a New Covenant, the full expression of the CoG now being manifested.Certainly their are differences between the church under the OT and NT.
So here is what I'm struggling with: You say there is one body of believers, OT and NT. "The saved under the OT are now included in it [the spiritual body of believers]." Do you believe that this inclusion is retroactive? In other words, do you believe that the elect of the OT are included in the body of Christ (the church, Col. 1:24) only after Christ? If so, by what righteousness was Abraham justified?
Have you considered Rom. 2:24-3:4:a?
"For circumcision is indeed profitable if you keep the law; but if you are a breaker of the law, your circumcision has become uncircumcision. Therefore, if an uncircumcised man keeps the righteous requirements of the law, will not his uncircumcision be counted as circumcision? And will not the physically uncircumcised, if he fulfills the law, judge you who, even with your written code and circumcision, are a transgressor of the law? For he is not a Jew who is one outwardly, nor is circumcision that which is outward in the flesh; but he is a Jew who is oneinwardly; and circumcision is that of the heart, in the Spirit, not in the letter; whose praise is not from men but from God. What advantage then has the Jew, or what is the profit of circumcision? Much in every way! Chiefly because to them were committed the oracles of God. For what if some did not believe? Will their unbelief make the faithfulness of God without effect? Certainly not! Indeed, let God be true but every man a liar."
These verses deal with both the physical aspects of those under the CoG as well as the spiritual. What was Paul trying to teach his NT hearers if there is the distinction you are making between the a) OT and NT body of believers and b) physical/spiritual?
Thank in advance for your help.