My micometer does not go big enough to get a perfect measurement, but when I placed a 5.3, ls6, and the 7.425 side by side I found that the 5.3 was the shortest. I think that would make it like this.
7.380=5.3
7.400=ls6
This is all comparing them by eye, but the 5.3 does look shorter.
The rain this weekend has kept me from finishing my cam install. When I do I will measure lifter pre-load and go from there.

 

Interesting, I've read here many times that all of the GENIII engines use the same size pushrod...I guess not. Word is that the longer valves in the LS6 heads compensate for the smaller base circle, but maybe the pushrod length is part of it too