The KJB 5 times uses holy Spirit, 1 time Holy Spirit, and 1 time holy spirit and uses Holy Ghost 90 times in 89 verses.

The holy Spirit is used 3 time in ASV, holy spirit not found

NKJV, holy Spirit 4 times, and holy spirit not found

NLT, NIV, Holy Spirit is used in all cases.

Why do you suppose they did this?
How important is it?

When perversion versions first started getting rooted in the church, they use to say it was just the way in the times they thought ghost was a spirit. I did not know better to answer that the King James Bible uses Holy Spirit also, but the real question what is the real difference?

I believe that Holy Ghost is used to ID the third person of the trinity.
The capitalization is questionable.