The first of the films, if I'm not mistaken (going on memory here) is "Murder with Pictures" (1936) with Lew Ayers. That's officially a 'Kent Murdock' book, but again, six-of-one, half-a-dozen of the other when it comes to Casey and/or Kent. I like the George Harmon Coxe films. B-Films all, with unnecessary comic relief, at least to modern viewers (and to me, if truth be told). They're not the same as the radio portrayal, but if a film has anything to do with radio, regardless of how tenuous that connection is, I'm predisposed to liking it. And if it takes place in a radio studio, then you've got me, no matter how bad the film may be.
As for "Dead Heat", the Edition Page (Copyright Page) states:
COPYRIGHT, 1950, BY COLUMBIA BROADCASTING SYSTEM AND GEORGE HARMON COXE
(Their capitals, not mine)
My wife and I listened to the surviving run of Casey faithfully, every Thursday, a couple of years ago, but as I've just finished my previous book and was sniffing around yesterday, undecided as to my next book, I'll read 'Dead Heat' and then re-listen to 'Pick-Up' and let you know how they compare, if you're at all interested.