I personally wouldn't run without the baffle or slinger with the high pinion, they help trap oil for the pinion bearings. As for the slinger it will be an issue if you need a smaller shim size for the new gears, that's way a food install kit comes with a new, thinner, slinger.
I used an East Coast Gear Supply (ECGS) master install kit which came with a new baffle and thinner slinger. Some people just throw them out, again personally I wouldn't. Maybe try calling ECGS, they might be able to send you the parts you need.