Does anyone know if a throttle body spacer will benefit an 8

My guess would be No.

I believe that a spacer is used to tune Runner length for specific rpms. Flow straightening and charge speed?

Both the V8 and the V12 have a Chamber after the throttle and then the Runners to the intake port. The V12 are the tubes crossing the top of the engine(Intake manifolds) and would be quite difficult to do any tuning on without a new casting.

The V8 versions are internal to the plastic intake manifold and are at max length now. The tube inlet is at the bottom of the side opposite the cylinder and the tube loops over the top and straight down to the port/valve.

It might be possible to simulate shortening them but making them appear longer would be near impossible