In a letter (#191) to To Tevis Clyde Smith, ca. February 1932, we learn that he was happy with the payment:

Oh, yes; I finally made Claytons’. I sold them a couple of yarns in a row, and while they kept me waiting awhile for the dough, they paid well when they did pay — $134 for one, and $144 for the other. Short stories too. I hope to gosh I can sell them a long novelet.

The first story was “People of the Dark” and the other one was “The Cairn on the Headland”.

The sale of the story to the Claytons is also mentioned in another letter (#195) to Tevis, circa March 1932:

Glad you liked the Roof business and the Sowers stuff. I’ve had quite a few praises on the Sowers thing, but don’t know whether they’ll get into the Souk. Likely not. Those yarns I sold Clayton were to their Strange Tales.

And at the end of a long letter (#220) to Lovecraft on November 2, 1932 he asks:

P.S. Have you read my “Cairn on the Headland” in the latest Strange Tales? If not, I’ll be glad to lend you my copy. It was the artist’s idea, not mine, to deck Odin in a solid steel cuirass!

Not happy with what the editor did with his story, he mention the story again in a letter to Lovecraft, circa December 1932:

I’m glad you liked the yarns mentioned. The editor took liberties with “The Cairn on the Headland”. In the original version, O’Brien was born in America. The editor changed this and made O’Brien a native of Ireland, but neglected to change the line: “We were countrymen in that we born in the same land.” That would seem to make “Ortali” an Irishman, too, when I intended him for an American-born Italian. In making Odin a purely evil spirit, I did that partly for dramatic effect, and partly because I was writing from the viewpoint of the ancient Irish. They must have considered that god an utter devil, considering the murdering, looting and destroying habits of his worshippers. Their shrines and monasteries were burned and demolished, their priests slaughtered, their young men and young women butchered on the altars of the one-eyed deity, and over all towered Odin. Seeing his effigy looming through the smoke of destruction and the flame of slaughter, dabbled with blood, and bestriding mangled corpses, the victims must have seen in him only the ultimate essence of evil.

Howard wrote to the Clayton Magazines (letter #247) on June 13, 1933:

A few weeks ago I wrote you asking a release of the British Empire rights on my stories, “People of the Dark” and “The Cairn on the Headland,” published in Strange Tales. I have had no reply from you.