Those illustrations are of the BIG trucks, the 8000 and 10000 Series 1956/57 trucks had the core support in the 6-cylinder position for the V8 engines and used the barrel shroud to make it work.
If you could find one It might still be too short because your radiator is thinner...It also looks like your fan is to far out, you need a longer spacer for it to work with that shroud.
Here's some pictures of my 1956 8400 with a SBC factory setup. It has a factory 4" thick radiator with the 7.25" deep shroud, the barrel is 21.5" across and I think it has a 20" fan.
Mike B
