Hello, Tim,

Chevrolet called it: 1955 2nd series or 1955 Truck Second Series

Look at the title of this Shop Manual
http://chevy.oldcarmanualproject.com/shop/1955truck2/index.htm

Look at the first couple intro pages of this Chevrolet Truck Specifications Manual:
http://www.1954advance-design.com/chev-specs/1955-Chevrolet-Truck-2nd-Series.pdf

I have never seen GM Chevrolet Truck documentation referring to a 1955.5 for a series of trucks or for an option.

Ask the facebook-scolder what GM Chevrolet Truck documentation used 1955.5
It would be nice to see/have that documentation.

What is the Facebook link?

GMC used different terminology/names/designators.

Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.