Newton Comics' The Incredible Hulk #2 carried an advertisement for the forthcoming Dracula series:
This appears to be a pre-production image. By the time Dracula #1 appeared it had earned a modified title - Tales of Horror:
The cover is recoloured from the US Tomb of Dracula #2:
The series begins with the story titled Dracula which originally appeared in the US Tomb of Dracula #1. The backup story was the 9-page Hobo's Lullaby from Vampire Tales #11.
Dracula #1 includes a colour Man-Thing poster drawn from the cover to the US Man-Thing #7. This poster appeared in other Newton Comics too - including The Incredible Hulk #2. The cover image was subsequently reprinted in Australia by Page Publications as The Man-Thing #3 and Monster of the Swamp.
Looking through the issue, it would appear conclusive that Dracula #1 was published early July 1975. Dracula #1 includes advertisements for The Fantastic Four #2 with an on-sale date of 12 July; The Avengers #2 and The Amazing Spider-Man #4 with on-sale dates of 19 July; Planet of the Apes #3 - no specified release date but the issue has a June 1975 cover date; and The Incredible Hulk #2 - no specified release date but advertised as On Sale Now; and the Dracula Contest on the rear cover has a cut-off date 4 August 1975..
The advertisement for Dracula #1 in The Incredible Hulk #2 advises that it will be available "early next month". If Dracula #1 was published July 1975, then it stands to reason The Incredible Hulk #2 was published June 1975. The Incredible Hulk #2 does not have a cover date, but it does carry advertisements for The Amazing Spider-Man #3 with an on-sale date 5 July; and The Fantastic Four #1, Planet of the Apes #2, and The Avengers #1 are all advertised as On Sale Now. Whilst I don't yet have precise release dates for these three issues, I'm sure they were all published before July 1975, all of which suggests The Incredible Hulk #2 was indeed published June 1975.
However, the kink in this triangulation is the note at the end of The Incredible Hulk #1 - on the last page it says "Don't miss Captain America in the next issue of The Incredible Hulk - on sale July 5". If that is correct, then it suggests that Dracula #1 was scheduled for publication early August 1975, not July 1975. And when the pre-production image is taken into account, it's not unreasonable to assume there may have been some delay in producing Dracula #1, which might push the release date to August 1975. Factoring in the Man-Thing poster common to both issues doesn't clarify the date issue for me as a case could be made for both July and August release dates on this basis.
I could speculate further - on possible delays and What Ifs for either issue - but overall, the weight of evidence leans towards a July 1975 publication date for Dracula #1, intended or not.
Update: Just had a quick look at The Avengers #2, which was published July 1975. The subscription page has Dracula added for a 12-issue subscription. It also includes an advertisement for Dracula #1:
This advertisement includes all the Newton stuff on the cover - the logo, the price, the Tales of Horror title, the No.1 Historic First Edition box - and it is advertised as On Sale Now. And the contest on the rear cover has a closing date of 4 August 1975. This clinches the July 1975 publication date for me.
Update 21/12/2018: Dracula #1 was advertised in the Sunday Observer 27 July 1975:
This is the first advertisement in the Sunday Observer for this series. It suggests 26 July 1975 as the publication date. The advertisements in this issue for other series clearly indicates an early July publication, however the timing of this advertisement is a strong indication the issue was delayed.
Note the reference to Dracula Lives!, and to Man Thing as The Swamp Creature. It is also interesting that this advertisement promotes the subscription service.