One issue with straight 8s is keeping the back end of the engine cool.
In terms of hot rods Greg, I suspect a few factors:
Before the Ford V8 hop up parts for the A& T flathead made making hop up stuff for the V8 a natural extension for those providers of Speed stuff.
The Ford V-8 was cheap to produce, relatively light & simple. Soon there was a decent supply of them in junk yards.
For similar reasons traditional hot rods have been largely Ford roadsters and coupes. While other v8s found their way into those cars a straight 8 in an A wouldn't be practical.
All obvious but just some thought as relates to Greg's comments.
For some reason when I think straight 8 I think locomotive like and when I think of Ford flat 8 and postwar ovh v8s I think more about a hot street car..
Cool thread for sure!