It's not possible to fit a big block on a small block engine holder, so I had to change the holder and file on the chassi. And it is still not perfect but I'm planning to make a few adjustments to make it fit better. If it was delivered with a big block they would need to make it beefier as well so the cost would probably decrease the sales. But in my opinion it should be delivered with a little smaller clutch bell to increase the low end power.