I'm currently at 24 references. On those I find 13 as being confirmed in the Apostolikon. 8 are unattested and regarded neutral in Kirby's reconstruction. 3 are red in Kirby's reconstruction, but according to the notes they are actually unattested with scholars who believe they are interpolations. They aren't actually confirmed as not being present by ancient sources.
Two of three in question are pretty major references in Mark. Here are the three in question:
Mark 04:11-12 Rom 11:7-8
Mark 12:16-17 Rom 13:6
Mark 13:32-37 1 Thes 5:2-6
Mark 4:
10 When he was alone, the Twelve and the others around him asked him about the parables. 11 He told them, “The secret of the kingdom of God has been given to you. But to those on the outside everything is said in parables 12 so that,
“‘they may be ever seeing but never perceiving,
and ever hearing but never understanding;
otherwise they might turn and be forgiven!’”
Romans 11:
7 What then? What the people of Israel sought so earnestly they did not obtain. The elect among them did, but the others were hardened, 8 as it is written:
“God gave them a spirit of stupor,
eyes that could not see
and ears that could not hear,
to this very day.”
BeDuhn:
Tertullian says with regard to the words of 11.33:
Whence that outburst? Out of his recollection of those scriptures to
which he had already referred, out of his mediation upon those types
and figures which he had previously expounded as bearing on the faith
of Christ which was to emerge from the Law. If Marcion has of set purpose
cut out these passages, what is this exclamation his apostle makes,
when he has no riches of his god to look upon, a poor god and needy as
one must be who has created nothing, prophesied nothing, in fact possessed
nothing, one who has come down to another’s property? (5.14.9)
Harnack (Marcion, 108*) maintains that this remark indicates that the
entirety of 10.5–11.32 was lacking in Marcion’s text, and that 11.33
directly commented on 10.4. Schmid (Marcion und sein Apostolos, 111)
expresses some doubt that the gap was so extensive. He points to a
passage in Ireneaus, Haer. 1.27.3, which refers to a Marcionite belief in
Christ’s descent into Hades, and suggests that this belief is based on
Rom 10.6–10. It is quite uncharacteristic of Schmid to credit anything
outside of the more systematic sources, and to rely, as he does here, on
an isolated comment about Marcionite teachings. I agree that explicit
reports about Marcionite interpretation and application of biblical passages
should be given tentative credit; but Irenaeus’ remark scarcely
rises to that standard, and Schmid’s suggestion cannot be accepted.
Mark 12:
14 And they came and said to him, “Teacher, we know that you are sincere, and show deference to no one; for you do not regard people with partiality, but teach the way of God in accordance with truth. Is it lawful to pay taxes to the emperor, or not? 15 Should we pay them, or should we not?” But knowing their hypocrisy, he said to them, “Why are you putting me to the test? Bring me a denarius and let me see it.” 16 And they brought one. Then he said to them, “Whose head is this, and whose title?” They answered, “The emperor’s.” 17 Jesus said to them, “Give to the emperor the things that are the emperor’s, and to God the things that are God’s.” And they were utterly amazed at him.
Romans 13:
6 For the same reason you also pay taxes, for the authorities are God’s servants, busy with this very thing. 7 Pay to all what is due them—taxes to whom taxes are due, revenue to whom revenue is due, respect to whom respect is due, honor to whom honor is due.
BeDuhn:
Rom 12.20–13.8a is unattested. Several researchers have suggested that
13.1–7 is an interpolation, among them Barnikol, “Römer 13,” and J.
Kallas, “Romans xiii.1–7: An Interpolation.”
Mark 13:
32 “But about that day or hour no one knows, neither the angels in heaven, nor the Son, but only the Father. 33 Beware, keep alert;[f] for you do not know when the time will come. 34 It is like a man going on a journey, when he leaves home and puts his slaves in charge, each with his work, and commands the doorkeeper to be on the watch. 35 Therefore, keep awake—for you do not know when the master of the house will come, in the evening, or at midnight, or at cockcrow, or at dawn, 36 or else he may find you asleep when he comes suddenly. 37 And what I say to you I say to all: Keep awake.”
1 Thess 5:
2 For you yourselves know very well that the day of the Lord will come like a thief in the night. 3 When they say, “There is peace and security,” then sudden destruction will come upon them, as labor pains come upon a pregnant woman, and there will be no escape! 4 But you, beloved, are not in darkness, for that day to surprise you like a thief; 5 for you are all children of light and children of the day; we are not of the night or of darkness. 6 So then let us not fall asleep as others do, but let us keep awake and be sober;
It seems to me that the exclusion of the last two sets of verses is pretty weak. They are really just unattested as far as I can see. I'm not sure what to make of the first comment, on Romans 11. Even that actually seems fairly weak. At the same time, that parallel between Mark and Paul is also questionable.BeDuhn:
1 Thess 4.18–5.18 is unattested. Friedrich, “1 Thessalonischer 5,1–11,”
has argued that the first eleven verses of chapter 5 constitute an
interpolation.
I was hoping for a decisive result here one way or the other, showing either that Mark was a witness to a pre-Marcionite orthodox collection or that Mark used a version that matched Marcion's. This leaves me a little bit in limbo, but right now I'm coming down on the side of Mark having used letters that match Marcion's. Given that I find no relation to 2 Thess, Colossians or Ephesians, I still think Mark was using a pre-Marcionite collection, but the question is whether the letters that matched Marcion's matched what Marcion used.
Granted, there aren't really that many confirmed differences between the two sets. One thing I do note is that it is confirmed that Marcion's Galatians listed the Jerusalem apostles as Peter (not Cephas), James, John, whereas the orthodox set lists James, Cephas, John. The Gospel of Mark of course uses Peter, not Cephas, and it introduces the disciples in the order Peter, James, John. So I'm looking at that as a point in favor of Mark having used a version that matches Marcion.