1. Word order:
The traditional text reads: Abraam ton patera hemon eurekenai kata sarka
Literally: Abraham the father of us to find concerning the flesh
The modern critical Greek text reads: eurekenai Abraam ton propatora hemon kata sarka
Literally: to find Abraham the forefather of us according to the flesh
External evidence: The traditional text is supported by the Majority of manuscripts. The modern critical text is supported by six Greek manuscripts (original hand of Sinaiticus, Alexandrinus, original hand of C, 81, 365, and 1506) and one or two translations (the Syriac Sahidic and possibly the Bohairic). There are also a handful of other Greek manuscripts that share the modern critical text word order, except for their use of the noun patera rather than propatora. Codex Vaticanus and one other Greek manuscript omit the infinitive eurekenai altogether. Thus, the RSV/NRSV/ESV tradition all have a note suggesting the possibility of the reading: "What shall we say about Abraham…."
Analysis: It certainly seems possible that a scribe might have accidentally written the infinitive eurekenai first and then "corrected" his mistake by adding the other words in the order. The verb might also have been omitted (as in B). There is no compelling reason to reject the traditional word order as attested in the vast majority of manuscripts.
Internal evidence: As we shall see below in the discussion of translation, a scribe might also have been motivated to "smooth out" the text by having kata sarka come behind the noun "father" to stress Abraham as the physical progenitor of the Jews.
2. Word variation:
The traditional text refers to Abraham as "father" (patera) and the modern text as "forefather" (propatora).
External Evidence: The textual evidence is divided as above with only six Greek manuscripts supporting propatora. It seems more likely, however, that a scribe might expand the meaning of "father" to "forefather" and less likely that one would diminish "forefather" to mere "father." Thus, "father" is the best reading.
3. Translation of kata sarka:
Here, the main question is whether the prepositional phrase "according to the flesh" should be read as modifying the noun "father" or the infinitive absolute verb "to find." Does it read: "what Abraham our father according to the flesh found" or "what Abraham our father found according to the flesh"?
If the former, Paul would be speaking to his fellow Jews and stressing their common physical heritage as Jews through their descent from Abraham, their "father according to the flesh." This translation is reflected in the NASB: "What then shall we say that Abraham, our forefather according to the flesh, has found?" and the ESV: "What then shall we say was gained by Abraham, our forefather according to the flesh?"
If the latter, then the kata sarka would relate to the verb. Thus, "What did Abraham our father find according to the flesh (according to physical things)?" What did Abraham discover regarding efforts at justification or gaining a right standing with God "according to the flesh" (i.e., through the efforts of the flesh)?
This is the translation reflected in the AV: "What shall we say then that Abraham our father, as pertaining to the flesh, hath found?" And also in the NIV: "What then shall we say that Abraham, our forefather, discovered in this matter?" Note, however, that the NIV prefers "forefather" to "father."
The latter appears to be the best option. This is especially the case when we consider that Paul is not merely speaking to Jews here but to Jews and Gentiles who have found a new identity in Christ, as is made clear later in the passage (see Romans 4:11 where Paul describes Abraham as the father of all who believe, both Jews and Gentiles). Thus, when Paul speak of Abraham as "our father" he is not saying that Abraham is the father of "we Jews" but of "we Christians (both Jews and Gentiles)."