Actually they've had hemis since the 60's. U ought to see a Plymouth Satelite with a 426 hemi in it, totally off the planet, and it was STOCK.
Those older hemis and even the new ones can pretty easily bolt up to a lot of trucks and cars. Real sleepers if ya do

Plus, they've had hemis in AA altered rail dragsters for years, I was part owner in one that used to run against Cha Cha Muldowney.