but the space should be thinner than that between other words in that line, as :
He's arrived by the Empire State Express.
The thinner space is intended to show that the short form of is or has should not be confounded with the possessive form of the pronouns.
It's the New York Central's fastest train.
Dialect matter, for which there can be no good authority but that of the author, should be spelled as written, even when the same word is abbreviated or contracted in different ways. It is unwise to attempt uniformity without a written code or permission from the author.
OLD-STYLE CONTRACTIONS
Quotations from obsolete authors, or reprints of old books or documents, or illustrative letters by illiterate people, should be accurate copies of the originals. Every fault of bad spelling, or misuse of capitals or italic, should be faithfully repeated to the minutest particular, so far as the types will allow. Old-style abbreviations with superior letters, such as wd, wh, ye, etc., are troublesome, and may lead to the dropping out of a superior letter which cannot be justified securely ; but they must be repeated unless a distinct order is given to spell out.