One of the most fascinating realities of the visions of Maria Valtorta in my view is that Jesus is very clear on his attitude towards non-Christians. Jesus confirms that if someone lives a just life, does good deeds and has faith in what they believe is the true one (whatever that is for them) they will be saved and will be allowed to enter heaven. He also confirms that after the end of the world, there will be only one heaven for all good humans, as there is only one God. What a powerful statement from God. But I think it is best to read yourself. Let me quote the passages here, with some pre-info. I marked the most important passages in bold: 

Jesus speaking to some of his disciples:

God Himself is Charity. Charity is but the most manifest and illustrative aspect of God. Of all His attributes Charity is the sovereign and original one, because all the other attributes of God originate from Charity. What is Power but active charity? What is Wisdom but teaching charity? What is Mercy but forgiving charity? What is Justice but ruling charity? And I could go on thus with regard to all the numberless attributes of God. Now, after what I have said, can you believe that he, who has no Charity, has God? No, he has not. Can you imagine that he may accept God, but not Charity? There is one Charity only and it embraces Creator and creatures and it is not possible to have only one half of it: that for the Creator, without having also the other half: that for our neighbour.

God is in His creatures. He is in them with His indelible sign, with His rights of Father, Spouse and King. The soul is His throne, the body His temple. Now he who does not love one of his brothers and despises him, holds in contempt, grieves and underestimates the Landlord of his brother’s house, the King, the Father, the Spouse of his brother, and it is natural that this great Being Who is Everything, and Who is present in a brother, in all brothers, should consider as given to Him the offence given to a lesser being, to a part created by Everything, that is to a single man. That is why I taught you the corporal and spiritual works of mercy, that is why I taught you not to scandalise your brothers, that is why I taught you not to judge, not to have contempt or to reject your brothers, whether they are good or not good, faithful or Gentiles, friends or enemies, rich or poor.

When on a nuptial bed a conception takes place, it is performed through the same action, whether it happens on a golden bed or on straw in a stable. And the creature which forms in a royal womb is not different from that which forms in the womb of a beggar. To conceive, to form a new being, is the same in every spot of the Earth, irrespective of parents’ religion. All creatures are born as Abel and Cain were born of Eve’s womb. And to the equality of conception, formation and manner of birth of the children of man and woman on the Earth, corresponds another equality in Heaven: the creation of a soul to be infused into the embryo, so that it may be the soul of a man and not of an animal, and it may accompany him from the moment of its creation until death, and may survive expecting the universal resurrection, when it will join the risen body and have with it a reward or a punishment. A reward or punishment according to the deeds accomplished in the earthly life. Do not think that Charity is unfair, and that only because many people do not belong to Israel or to Christ, although they are virtuous in the religion which they follow convinced that it is the true one, they are to remain for ever without reward. 

After the end of the world no other virtue will survive except Charity, that is, the Union of all the creatures who lived in justice, with the Creator. There will not be several Heavens: one for Israel, one for Christians, one for Catholics, one for Gentiles, one for heathens. There will be one Heaven only. And likewise there will be one reward only: God, the Creator, Who rejoins His creatures who lived according to justice, and in whom, because of the beauty of the souls and bodies of saints, He will admire Himself with the joy of Father and of God. There will be one Lord only. Not one Lord for Israel, one for Catholicism, one for each of the other religions. 

I will now reveal a great truth to you. Remember it. Hand it down to your successors. Do not always wait for the Holy Spirit to clarify the truth after years or centuries of darkness. Listen. You may say: “Then, what justice is there in belonging to the holy religion, if at the end of the world we shall be treated exactly as the Gentiles?” I reply to you: the same justice which there is and it is true justice − for those who, although they belong to the holy religion, will not be beatified, because they they did not lead a holy life. A virtuous heathen, only because he lived according to choice virtue, convinced that his religion was good, will have Heaven at the end. When? At the end of the world, when of the four abodes of the dead, two only will remain: that is, Paradise and Hell. Because Justice, at that time, will only be able to keep and give the two eternal kingdoms to those, who from the tree of free will, chose good fruits or wanted wicked ones. But what a long expectation before a virtuous heathen achieves that reward!… Do You not think so? And that expectation, particularly from the moment when Redemption will have taken place with all its consequent wonders and the Gospel will have been preached all over the world, will be the purgation of the souls which lived with justice in other religions, but were not able to enter the true Faith, after they became acquainted with its existence and the proof of its reality. Their abode will be Limbo for centuries and centuries, until the end of the world. The believers in the true God, who were not heroically holy, will have a long Purgatory, which may last until the end of the world for some of them. But after expiating and waiting, the good, irrespective of their provenance, will all sit at the right hand of God; the wicked, whichever their provenance may be, at the left hand and then in the dreadful Hell, while the Saviour will enter the eternal Kingdom with all the good souls.” Maria Valtorta, The Poem of the Mangod, chapter 442. Jesus Speaks of Charity to the Apostles.