Shane,
I'd say that 235 engine out of a 1958 car is worth your while.
Have you checked any numbers from that engine to verify it is a 58 235?
Although cars had a hydraulic cam, and trucks had a mechanical cam,
they both used the same blocks from 58-62.
So it is possible that a 58 car block could have the same block casting number as your 59 truck.
The difference would be the casting date code.
Also, from 58-62, some trucks had front side mounts while others had the front center mount.
Have you seen the Resto Pack
http://chevy.oldcarmanualproject.com/chevyresto/59index.htmIf you've messed with V-8's, you're gonna love the 235.
Good luck with your restoration.