Of course, the Holy Spirit did already exist for eternity. The YLT is of course had some trouble translating it from Greek and was wrong in this regard. The KJV translators may not have found it in the Greek so they put in italics. Italics though sometimes were to complete the sense but that is only one thing use of the Italics. Italics in the KJV also means that it is found in other language other than the Greek for the NT. Evidences why the word was there because they found via Latin, French and other known languages where they compare and even previous English translation. The Wessex Gospel 1175c are the oldest translations into English without the Latin and where we can find “given” and this might answer your dilemma.First, I admit that I think I know the answer to this question. So I'm using it as a provocation to discussion on it. In John 7:39 the King James renders it; "(But this spake he of the Spirit, which they that believe on him should receive: for the Holy Ghost was not yet given; because that Jesus was not yet glorified)". But the word "given" is in italics to show that the word does not appear in the original texts. Thus, Darby (correctly) renders this verse;
"But this he said concerning the Spirit, which they that believed on him were about to receive; for [the] Spirit was not yet, because Jesus had not yet been glorified." (Darby)
But immediately a difficulty arises. The meaning of the verse changes dramaticaly. It now means that the Holy Spirit, which the Disciples received in John 20:22) did not exist yet in John 7:39! Young's literla translation agrees with Darby. It reads;
"and this he said of the Spirit, which those believing in him were about to receive; for not yet was the Holy Spirit, because Jesus was not yet glorified" (YLT)
What then is the truth? Was the Holy Spirit "not yet" - that is, He did not exist yet until Christ's resurrection?
The gospels are written in the Old English West Anglo-Saxon dialect of Northumbria. Desiderius Erasmus had access to these MSS before starting his translation of the Textus Receptus. In the five years prior to starting his translation work Erasmus was Professor of Divinity at Cambridge at a time when the university's benefactors owned these manuscripts.
The King James Bible translators had access to these manuscripts. All the six KJV translation companies where housed at Oxford, Cambridge and Westminster and all had access to the Wessex Gospels.
http://textusreceptusbibles.com/Wessex/43/7
John 7:39
:39
Ðæt he cwæð be þam gaste þe þa scolden under-fon þe on hym ge-lyfden. Ða get nes se gast ge-seald. for-þam þe se hælend næs þa gyt ge-wuldrod.The OE “ge-seald” is a preterite tense of “ġesellende” from “gesellan” means 1. to give 2. to grant or bestow (as by God) 3. to deliver ; hand to 4. to hand over 5. to give in exchange 6. to give what may be demanded; to pay tribute ; tax ; fine or compensation 7. to give up ; surrender ; lose 8. to give forth or put forth words or statements; to make sound 9. to offer ; present ; or show for consideration 10. to assign ; appoint 11. to make have
https://www.oldenglishtranslator.co.uk/
The KJV of course is in no doubt correct in the matter including numerous English bibles where they have not put in italics.