I have never heard of a GOOD reason to run a gear drive in any V8 engine. You need to run an idler gear to keep the camshaft rotation correct and I don't think this added complexity makes up for any gains in performance or durability.
Crankshaft harmonics (the pistons bending the crankshaft during each firing)works against gear reliability and a jet pump may add more harmonics to the crankshaft. Harmonics has no effect on timing sprockets and a chain.
The balancer, on the front, and the flywheel, on the rear, help to cancel crankshaft harmonics but many people run jets without a flywheel (using only a flexplate). A flexplate only cancels harmonics if it has a torque converter attached to it (like in a car or truck).
Dennis Moore