Herminator

The Cuda has always tended to be louder than other tourers but you can do some things to quieten it down.
Shim the diffs more to one side to make the mesh looser.
Shim the small bevel gears so they have no back and forth movement in the shaft holders.
New gears run in with a slow motor on a few volts.
Remove the diff covers, they make a noisey car sound like a tractor.

I run without the gear covers all the time and stones are not a big problem. I get the occasional tiny stone stuck in gear teeth but a quick look to see where it is then flick it out with a screw driver and everything is fine. You just end up with a few chewed up gears, but the Cuda gears are beefy enough to run fine with a few chunks out of them. I've had stones in gears even when running the covers and then it's a pain in the backside to get to the problem, you're not even sure if it's the front or rear so end up dismantling half the car

Shimming the diffs is a bit of an art I find, a big part of making things quiet. One shim too few and it may seem like there is minimal play but it will still be noisey. One shim too many and it will have no play but still spin fairly freely (not as free as it should be though) and it will again be noisey. So you need to take the bulkheads off and on a few times and use trial and error.

Maybe Dave will be nice and find the pic he had of the small bevel gears, showing the differeces that meant different shimming for each and he can tell us the thickness of shims he uses for each while he's at it
I tend to guestimate these at the moment, since taking them apart without damage is a pain, when they're in the shaft holders they stay there until they're deformed and ready for the bin
(oddly though I have a nice little collection of used bevel gears, I don't know why I keep so many "emergency backup" spares it's the same with spurs and stripped thread steering knuckles )