You have a number of variables here depending on year and engine. 55-57 core supports have different locations for V-8 and 6 cyl trucks. A V-8 in a truck with a 6cyl core support would likely need a different shroud than the stock V-8 application. I believe 58-59 trucks had the same core support for V-8's & 6's and the V-8's used the factory shroud.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine