Z-bar too narrow?

Nick I said
Do you think a torque strap is still necessary for a motor only making 400 hp and 435 torque (optimal dyno conditions) at the flywheel?

yes, IDK, probably yes
yes on the stock biscuit mounts
IDK on the Mancini-mounts
383s and manual transmissions are hard on mounts. the strap is cheap insurance.