It's about 19 secs for a late '60's A-body bone stock, seriously....I guess if the truck had the perfect gears it'd do 20 secs,...lucky to be goin' 70 by then....
My dead stock all factory original 66 Valiant, slant and three-on-the-tree went a best of 19.8 in the 1/4. I have an 82 D150, slant with 833 OD but unfortunately it was a dead dog when I got it. I will be able to post some numbers in a few weeks when it's ready to get back on the street, but it's a lightly warmed up slant. Given it's pushing a heavy brick, I imagine about the same times or worse.