Although the other renderings are possible

who is over all, God — rather, “God over all.”
blessed for ever. Amen — To get rid of the bright testimony here borne to the supreme divinity of Christ, various expedients have been adopted: (1) To place a period, either after the words “concerning the flesh Christ came,” rendering the next clause as a doxology to the Father - “God who is over all be blessed for ever”; or after the word “all” - thus, “Christ came, who is over all: God be blessed.“, etc. [Erasmus, Locke, Fritzsche, Meyer, Jowett, etc.]. But it is fatal to this view, as even Socinus admits, that in other Scripture doxologies the word “Blessed” precedes the name of God on whom the blessing is invoked (thus: “Blessed be God,” Psa_68:35; “Blessed be the Lord God, the God of Israel,” Psa_72:18). Besides, any such doxology here would be “unmeaning and frigid in the extreme”; the sad subject on which he was entering suggesting anything but a doxology, even in connection with Christ’s Incarnation [Alford]. (2) To transpose the words rendered “who is”; in which case the rendering would be, “whose (that is, the fathers’) is Christ according to the flesh” [Crellius, Whiston, Taylor, Whitby]. But this is a desperate expedient, in the face of all manuscript authority; as is also the conjecture of Grotius and others, that the word “God” should be omitted from the text. It remains then, that we have here no doxology at all, but a naked statement of fact, that while Christ is “of” the Israelitish nation “as concerning the flesh,” He is, in another respect, “God over all, blessed for ever.” (In 2Co_11:31 the very Greek phrase which is here rendered “who is,” is used in the same sense; and compare Rom_1:25, Greek). In this view of the passage, as a testimony to the supreme divinity of Christ, besides all the orthodox fathers, some of the ablest modern critics concur [Bengel, Tholuck, Stuart, Olshausen, Philippi, Alford, etc.]

Whose are the fathers, and of whom as concerning the flesh Christ came, who is over all, God blessed for ever. Amen.
(KJV)
of whom are the fathers, and from whom, according to the flesh, Christ came, who is over all, God blessed for ever. Amen.
(KJ21)
Whose are the fathers, and of whom as concerning the flesh Christ came, who is over all, God blessed for ever. Amen.
(AKJV)
whose are the fathers, and of whom is the Christ according to flesh, He being God over all, blessed forever. Amen.
(MKJV)