Acts 7:44 Our fathers had the tabernacle of witness in the wilderness, as he had appointed, speaking unto Moses, that he should make it according to the fashion that he had seen. 45 Which also our fathers that came after brought in with Jesus into the possession of the Gentiles, whom God drave out before the face of our fathers, unto the days of David;

Hebrews 4:7  Again, he limiteth a certain day, saying in David, To day, after so long a time; as it is said, To day if ye will hear his voice, harden not your hearts. 8 For if Jesus had given them rest, then would he not afterward have spoken of another day.

Again, the context reveals that this scripture is referring to Joshua, the son of Nun and not the Messiah. All other translations put "Joshua" here. Why then is it translated 'Jesus'? The answer lies in the Greek/Latin corruption of the Messiah's original Hebrew name. Originally, the name of the Messiah was יהושע, pronounced Yahoshua. This is the Messiah's original name. When the Gentiles tried to transliterate His name into Greek, they came up with ihsoun or "Iesous". This word was from #3091 (Strong's - 2424. Iesous ee-ay-sooce' of Hebrew origin (3091); Jesus (i.e. Jehoshua), the name of our Lord and two (three) other Israelites:--Jesus.)  in the Hebrew which is יהושע .

When Iesous was transliterated into Latin, it became "Iesus", which was then carried over into English it became our modern day "Jesus" when the letter "J" developed. 

Therefore, the reason the KJV has "Jesus" in those two verses is because the Messiah's name is actually the same name as Joshua, Son of Nun... correctly pronounced "Yahoshua".

References

Barnes' notes: (Note on Matt. 1:21)

"His name is Jesus: The name Jesus is the same as Saviour. It is derived from the verb signifying to save. In Hebrew it is the same as Joshua. In two places [Acts 7:45 and Hebrews 4:8] in the New Testament it is used where is means Joshua, the leader of the Jews into Canaan, and in our translation the name Joshua should have been retained."

Catholic Encyclopedia:

"The Sacred Name ---- The word Jesus is the Latin form of the Greek "Iesous" which in turn is the transliteration of the Hebrew Jeshua, or Joshua, or again Jehoshua, meaning 'Jehovah is Salvation' " Vol. 8, p. 374

Encyclopedia Americana:

"Jesus Christ--- ...Although Matthew (1:21) interprets the name originally Joshua, that is, 'Yahweh is Salvation,' and finds it specially appropriate for Jesus of Nazareth, it was a common one at that time." (Vol.16, p. 41)

Encyclopedia Britannica (15th ed.)

"Jesus Christ---...The same is true of the name Jesus. In the Septuagint it is the customary Greek form for the common Hebrew name Joshua;" (Vol. 10 p.149)

Encyclopedic Dictionary of Religion:

"Jesus (The Name) --- Matthew's gospel explains it as symbolic of His mission, 'For he will save His people from their sins.' This agrees with the popular meaning as 'Yahweh saves...' " p.1886

Interpreter's Bible: (Note on Matt. 1:21)

"Jesus: for He shall save: The play on words (Yeshua, Jesus; yoshia, shall save) is possible in Hebrew but not in Aramaic. The name Joshua means "Yahweh is salvation"

Matthew Henry's Commentary

(on Matthew 1:21)

"Jesus is the same name with Joshua, the termination only being changed, for the sake of conforming it to the Greek

Smith's Bible Dictionary:

"Jesus Christ ---- The name Jesus means Savior, and was a common name, derived from the ancient Hebrew Jehoshua."