I have heard that while a Muslim body is in a pig's body, his soul is prevented from reaching paradise. Is this true or false?
First of all:
I would like to get sources about this topic.
You haven't even mentioned sources that is holding up your statement or question. And you want sources or evidences against it?
Sometimes, we as humans, should be able to filter out questions that really doesn't make any sense. If not, you will have ten million questions in your head and only 5 of them make any sense. To start looking for sources or making a research for such questions would just be a waste of time.
And as American Muslim said "you clearly haven't done any investigation."
To your question
As Muslims we do not believe a person is prevented to enter the paradise if someone doing something bad on you.
Say: What! shall I seek a Lord other than Allah? And He is the Lord of all things; and no soul earns (evil) but against itself, and no bearer of burden shall bear the burden of another; then to your Lord is your return, so He will inform you of that in which you differed.
And when they hear idle talk they turn aside from it and say: We shall have our deeds and you shall have your deeds; peace be on you, we do not desire the ignorant.
We are not going to get punished because someone else doing something to us. By other words, it is a false statement.
Now this answer can be made much longer, if we get in details and about the opinions about the soul and paradise and such. by knowing that, it may have prevented you from asking a question like this. As I understood, that is not your intention with your question. You could do research on that. I highly recommend you to read some logic too.
In the name of Allah, the most Gracious, the most Merciful
Whereas you have asked in your question that "- true or false?" As below:
Putting a Muslim body in the pig's body prevent his soul to go to paradise - true or false?
As a consequence, it can be presented as the answer of you question that is it "False". Because to the best of my knowledge, and likewise as much as I researched, there is not such issue based on my researches.
And Allah knows the best