They're big on the Ford 6's as well as slant 6's, too, from what I understand. GM never offered a V-8 in Brazilian-produced GM products, so the 250 has a long, rich history of modifications and racing in Brazil. There's even companies in South America that produce billet blocks, exotic cylinder heads, etc., for the GM 250.
Ford offered the 302 and Chrysler offered the 318 in Brazilian products, but from what i understand, I-6 production still heavily outweighed the V-8 option in both product lines.
What's extra impressive (to me, anyway) is that the cars featured in the video still utilize OEM production cast iron engine block and cylinder head castings. Awesome stuff!!