Alex Toth's His Back to the Wall was originally published in Western Gunfighters #24, February 1957.
It was reprinted by Horwitz Publications in Giant Gunsmoke Western #5 c.March 1959 under a Maurice Bramley cover:
It was also published in Australia in Page Publications' Gunshot Western Library #24 c.May 1971.
I suspect this was requested because the GCD does not list any reprints of this story. I nevertheless expect that it is available in various comics and Toth collections, just as I expect it to turn up in other Australian editions by Horwitz and Page Publications. Regardless, if this has been on your wish list too - enjoy!