I believe in Post-Tribulation Rapture. The most important reason is 1 Thessalonians 4. It says the saints are raptured up after the Lord descends, which means the Rapture is not only Post-Tribulation, but also Post-Resurrection, and Post-Second-Coming i.e. on the Last Day.
"Believers Who Have Died
13 Brothers and sisters, we do not want you to be uninformed about those who sleep in death, so that you do not grieve like the rest of mankind, who have no hope. 14 For we believe that Jesus died and rose again, and so we believe that God will bring with Jesus those who have fallen asleep in him. 15 According to the Lord’s word, we tell you that [1] we who are still alive, who are left until the coming of the Lord, will certainly not precede those who have fallen asleep. 16 For [2] the Lord himself will come down from heaven, with a loud command, with the voice of the archangel and with the trumpet call of God, and [3] the dead in Christ will rise first. 17 After that, we who are still alive and are left will be caught up together with them in the clouds to meet the Lord in the air. And so we will be with the Lord forever. 18 Therefore encourage one another with these words."
So this is the sequence.
[1] We who are alive will not precede those who have fallen asleep.
[2] For first of all, the Lord Himself will come down from Heaven loudly.
[3] Then after this, the Resurrection of the righteous dead, i.e. the Saints.
[4] And only after the Lord's Coming, and Saint's Resurrection, the Rapture.
[5] The Rapture means we will receive Resurrection bodies without dying.
I.e. to say the last generation of saints on Earth will not need to die to receive glorified Resurrection bodies. This is clear in 1 Cor 15:
50 I declare to you, brothers and sisters, that flesh and blood cannot inherit the kingdom of God, nor does the perishable inherit the imperishable. 51 Listen, I tell you a mystery: We will not all sleep, but we will all be changed— 52 in a flash, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, the dead will be raised imperishable, and we will be changed. 53 For the perishable must clothe itself with the imperishable, and the mortal with immortality. 54 When the perishable has been clothed with the imperishable, and the mortal with immortality, then the saying that is written will come true: “Death has been swallowed up in victory.” Again, if you compare the two verses, it is very clear. St. Paul the Apostle teaches us that [1] We will not all sleep, but we will all be changed, which means those who witness the Rapture will receive Resurrection bodies without dying, but[2] First of all, the trumpet will loudly sound, and then [3] the Dead will be raised Imperishable, and only then [4] we will be changed at the end.
Hence, the Scriptural Witness is imho clear about a Post-Trib Rapture. God Bless.