Actually in a C-90, the most popular engine was the 6-71, second most popular the 8V-71. The 6V-53 was mostly in C-70's.
It's true about the 318 meaning CID on a 6V-53. But for some reason, the truckers, way back when, started nick-naming the 8V-71 a "318" as it is the horse power of one as you have mentioned.
