An article in the 11/66 issue of Ramparts mentioned an abortive attempt by Mark Lane to interview Benavides.
Earlier this year Mark Lane located Domingo Benavides, a witness to the shooting whose brother was mysteriously killed (see above), and arranged to meet him at Lane's motel for a filmed interview the next morning; Lane offered him $100. That night two men from the homicide squad came to the motel and inquired of Lane's film crew why they were so interested in Benavides. "What did you offer our boy $100 for?" they asked. According to the film crew, the policemen knew the exact time of Benavides' appointment with Lane, implied Benavides would not be there, and generally showed a great deal more concern about their footage on the Tippit murder than about the killing of Kennedy. Benavides never showed up.
Ramparts Magazine
The Legacy of Penn Jones, Jr. by David Welsh p.47

Sounds sinister but there's no mystery as to the source of the information supplied to the policemen of the homicide squad. After dropping a dime & spilling the beans Benavides was instructed by his handlers to stay away from Lane.

This item about Tatum appears in the Tippit material available at Dealey Plaza UK. From Bill Pulte's 2/99 letter to Harrison Livingstone:
Tatum and the used car dealers are critical to Myers' case. But there isn't a shred of evidence that Jack Tatum was actually there, and Warren Reynolds told his close friend Mack Pate that he was closer than any other of the car dealer employees to the suspect but not close enough to have any idea who it was.

And there's this:
Greg Lowrey asked everyone he could find who had [been] at the scene of Tippit's murder to describe everything they saw.. A lot of details were described by two or more people independently. Greg has written hundreds of pages based on these interviews. What he did is encyclopedic. So, when he doesn't find in his interviews any references to anyone who looks like Tatum, who did what Tatum claims to have done, and who drove a vehicle like Tatum's, it is pretty clear that Tatum wasn't there.
[Tippit 1.pdf p.8]

The straightforward way to refute the contention that "Tatum wasn't there" is to provide "a shred of evidence" that he was, an uncompleted task.

More on Reynolds to come at some point. In the meantime, given the intrinsic merit of Lowery's method, access to his encyclopedic material would be very welcome, but I'm coming up empty so far. Help will be appreciated.