question about 77 chevy's

[68GMC454]

looking at a 77 chevy 1/2 long bed with a 454 400 turbo.....was this factory or has it been changed over somewhere along the line.......i found the truck on line an havent seen it in person yet, but plane on looking at it in the next day or so... price is 800.00,

but he has another 74 that the body looks real clean, but it only has a 350 in it.. both of them are 800.00 each... to many trucks to look at an no money to buy them all,,lol.........

but im more interested in the 77 with the 454...oh yeah its a LWB truck