The 1958 Vehicle Info Kit shows two HP ratings for the 235 engine. Conventional trucks were rated at 145 gross HP @4200 rpm with a "Thriftmaster Conventional Truck Engine", while Forward Control Trucks were rated at 135 gross HP @4000 rpm with a "Thriftmaster Special 6-Cylinder Engine".
The basic engine was the same as the cars, except for bolt-on stuff like BC59 mentioned with the updraft carb.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.