Unlike Circuit Breaker, Death's Head would actually be owned by Hasbro and not Marvel (if Hasbro cared enough to do some research about it.)
It's alleged by Marvel that 'High Noon Tex' was a one-page strip that (like Circuit Breaker's appearance in Secret Wars II) appeared in other Marvel UK books before Death's Head's first appearance in Transformers UK #113. This is, however, untrue. 'High Noon Tex' was never published anywhere before Transformers #113 in May 1987 (in fact, '...Tex' didn't even exist back then.) The one-page 'High Noon Tex' strip didn't run until well over a year later - in September of 1988. It was damage control - well after Death's Head's popularity in his Transformers appearances - that 'High Noon Tex' was produced as an argument that he was a Marvel character rather than a Hasbro one (so the Marvel UK Death's Head series could run without Hasbro having a hand in it.) This is further evident by the fact that 'High Noon Tex' was drawn not by Geoff Senior, who - as we know - created Death's Head and drew his first appearances in Transformers comics, but by Bryan Hitch, who drew the Death's Head series as of December of 1988. The signature in the corner of 'Tex' even says "Hitch '88". If 'High Noon Tex' was in fact done in, say, April of 1987 then it would also be Hitch's first published comics work, predating his supposedly 'actual' first comics work by a couple of months, back when he was seventeen years old. In the Incomplete Death's Head #1 from 1993 it states Re: 'High Noon Tex' that "the main energies behind this historic page were Simon Furman, Bryan Hitch and former UK Editor Richard Starkings". Richard Starkings was not the editor of Transformers UK #113 - Ian Rimmer was; Bryan Hitch was not the artist of Transformers #113 - Geoff Senior was. However, both Richard Starkings and Bryan Hitch perform those roles over a year later on Death's Head the series.
The claims that 'High Noon Tex' came first are either accidentally misremembered or deliberately misleading because Marvel realised they needed to secure the ownership of Death's Head. Also unlike Circuit Breaker, whose Transformers appearances always contained the disclaimer "CIRCUIT BREAKER and the distinctive likenesses thereof is a trademark of the Marvel Entertainment Group Inc" none of Death's Head's Transformers issues had a similar disclaimer - he was always under the blanket of the Hasbro. Surely if Marvel had gone to all the 'High Noon Tex' trouble to secure Death's Head for their own then they would have stuck it in the legal blurb at the beginning of the comics. At worst, 'High Noon Tex' was a Marvel Comics smokescreen attempt to anachronistically secure copyright for a character that they wouldn't otherwise have in order to begin the Death's Head solo comic.
'High Noon Tex' was not published before Transformers #113 (May, 1987) - nobody has ever seen '...Tex' in anything published before September 1988; it's signed 'Hitch 1988' and Hitch was a seventeen year-old who wasn't working in comics at the time of Transformers #113. There is no physical evidence that a teenager with no comics work who wasn't Geoff Senior drew 'High Noon Tex' before May of 1987 and that that particular teenager coincidentally ended up drawing Death's Head as a series one-and-a-half years later. 'High Noon Tex' was not published before Transformers #113 - nobody has ever seen a copy printed in 1987 and it's even signed 1988. It's an 'urban' legend.
(The '88 signature from 'High Noon Tex'. And yes, if you just read my whole rant above, I am kind of obsessive about this issue - it's a personal pet peeve of mine, thanks.)