By 58, the low water pump engine was already in both cars and trucks- - - -the high pump 235 only applies to 54 and early 55 trucks. The hood height and core support for the later engine was the reason for the low mount pump. Not sure about shaft length, but a quick look at the truck engine that's being replaces will answer that question.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!