All the dispensationalists that I know and associate with believe that there has only been one way for salvatioon/justification.
Since the fall of man, God has been graceous to provide a way for that. It has ALWAYS been by FAITH. FAITH in believing/doing what God required at that point in time in human history.
Under the Law FAITH was demonstrated by doing the deed/works of the Law by FAITH. In this dispensation of grace, in which we now live, Salvation/justification is by FAITH ALONE in the Cross work (death, burial, and resurrection) of Christ.
THANKS for asking.
God Bless.
Live Well, Laugh Often and Love the Lord!
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Well stated,Dispy. And perhaps another consideration is "the content of faith" that was required in different dispensations.
What was the "content" of faith required to be believed during Matthew-John, and "early" Acts?

bold is my emphasis):
"Then they that were in the ship came and worshipped him, saying, Of a truth
thou art the Son of God." Mt. 14:33
"And Simon Peter answered and said,
Thou art the Christ, the Son of the living God." Mt. 16:16
(comment: and with the 16:18 "upon this rock" statement by the Lord Jesus Christ, our Saviour was setting the "foundation", i.e., the "rock", upon which the kingdom church, the "little flock" church(Luke 12:32 )would be built upon-their faith would rest upon the foundation that He was "
the Christ, the Son of the living God.")
"And he saith unto them, But whom say ye that I am? And Peter answereth and saith unto him,
Thou art the Christ." Mark 8:29
"He said unto them, But whom say ye that I am? Peter answering said,
The Christ of God." Luke 9:20
"But as many as received him, to them gave he power to become the sons of God, even to them
that believe on his name." Jn. 1:12
"Now when he was in Jerusalem at the passover, in the feast day, many
believed in his name, when they saw the miracles which he did." Jn. 2:23
"He that
believeth on him is not condemned: but he that believeth not is condemned already, because he hath not
believed in the name of the only begotten Son of God." Jn. 3:18
"And said unto the woman, Now
we believe, not because of thy saying: for we have heard him ourselves, and know
that this is indeed the Christ, the Saviour of the world." Jn 4:42
"And we
believe and are sure that thou art that Christ, the Son of the living God." Jn. 6:69
"She saith unto him, Yea, Lord:
I believe that thou art the Christ, the Son of God, which should come into the world." Jn. 11:27
"
But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name." Jn. 20:31
No change in the message in "early" Acts:
"Therefore let all the house of Israel know assuredly, that God hath made the same Jesus, whom ye have crucified, both
Lord and Christ." Acts 2:36
"And his name
through faith in his name hath made this man strong, whom ye see and know: yea, the faith which is by him hath given him this perfect soundness in the presence of you all." Acts 3:16
"Be it known unto you all, and to all the people of Israel, that
by the name of Jesus Christ of Nazareth, whom ye crucified, whom God raised from the dead, even by him doth this man stand here before you whole." Acts 4:10
"Neither is there salvation in any other: for there is
none other name under heaven given among men, whereby we must be saved." Acts 4:12
"And daily in the temple, and in every house, they ceased not to
teach and
preach Jesus Christ." Acts 4:42
"And Philip said, If thou believest with all thine heart, thou mayest. And he answered and said, I believe that
Jesus Christ is the Son of God." Acts 8:37
No change in the message by Paul,
early in his ministry, before he was progressively/gradually(i.e.,
progressive revelation:Acts 9:9,16; 22:10,16,17("trance"); 26:16; 1 Cor. 11:23; 2 Cor. 12:1 ; Gal. 2:2; Eph. 3:3; Col. 1:25; "But now"-Romans 16:26, Eph. 2:13, Col. 1:26 / notice Paul spent 3 years in Arabia per Galatians 1:17,18! 3 years! I find this amazing! Could that be Mt. Sinai? ) given the revelation of the mystery, from the risen, ascended, and glorified Lord Jesus Christ, from heaven(not earth),and the prophetic program was progressively/gradually(but temporarily) set aside:
"And straightway he
preached Christ in the synagogues,
that he is the Son of God." Acts 9:20
"But Saul increased the more in strength, and confounded the Jews which dwelt at Damascus, proving
that this is very Christ." Acts 9:22
Notice the change in Acts 13:
Paul presents the "outline" of 1 Cor. 15:1-4, the only gospel that will save in the current dispensation we are under :
Verse 13:28:"And though they found no cause of death in him, yet desired they Pilate that he
should be slain." = the
death of the Lord Jesus Christ
Verse 13:29: "And when they had fulfilled all that was written of him, they took him down from the tree, and
laid him in a sepulchre."=the
burial of the Lord Jesus Christ
Verse 13:30: "But God
raised him from the dead:..." =the
resurrection of the Lord Jesus Christ
And notice the gradual change in the message, as Paul boldly states:
"Be it known unto you therefore, men and brethren, that through this man is preached unto you the forgiveness of sins: And by him all that believe are justified from all things, from which ye could not be justified by the law of Moses." Acts 13:38,39
In Christ,
John M. Whalen