eslHQ - come true

It's really difficult to comment on sentences like this without knowing the context. I've googled it and checked the most common corpora but can't find it...

Anyway, without a context, the word that actually strikes me as most strange is "literal". How can you have a literal dream - whether the word is being used to mean a nighttime dream or hoped for the future (as I presume it is here), it doesn't seem to make any sense. Again, the corpora show no instances of literal and dream ever collocating.

But to your question....

The most natural version would certainly be This is a dream come true meaning This is a dream which has come true , with which and has elided.

The use of having would indicate something like as it had come true or when it had come true. For example:

His dream having come true, he suddenly found himself with nothing more to aim for.
ie meaning As his dream had come true, he suddenly... etc.

So having doesn't seem to fit in your sentence, where the writer undoubtedly means which has come true. With more context it might be possible, but I can't really think of one that would make it sound natural.