Flashback Radio: Fantastic Four (1975)

The short-lived Fantastic Four radio program debuted in 1975 and ran for 13. It adapts 13 issues of comic and featured a young Bill Murray as Johnny Storm!

The style of the show is somewhere between Old Time Radio and an audiobook, meaning it has a full cast and sound effects, but relies much more on narration than is typical of OTR. 

The entire show can be found several places on the internet, but here it is on Youtube:

Flashback Radio: The Adventures of Doc Savage (1985)

In 1985, NPR ran a Doc Savage serial in the style of old-time radio. The series adapted two of the original novels by Lester Dent Fear Cay and The Thousand-Headed Man, in 13 episodes. The latter adaptation was done by Will Murray, who has also penned original Doc Savage novels.

The series was released on CD by Radio Archives, but it also appears to be available on a couple of places on the internet, including here.