I used a tubular style mount to fit a 455 Buick in my panel truck.

I modified a tube mount that was for a 460 Ford in a F100 truck!
It allowed a nice low, set back & I was able to use the stock cast iron
exhaust manifolds, too.

As the others here have stated ... it adds a bit of additional stiffness to the frame; esp. when putting in one of these torque monsters.