I had to reply to this one as it happened to us - the 96 should have a cross drilled gear but I have seen 98's without
Anyway the input gear will only solve the clunking - worn shaft splines, but the whine are the gears not meshing correctly
The 230 is a swine to shim up = we put a set of Ashcroft high ratio gears in a 300 not so long ago and the output shaft (to the prop shafts) has so much play it was un true
We did the maths and had to fit a 0.60 inch shim to take up the play
When you have 2 x taper roller bearings on a shaft and very loose, then there is more play on the shaft, thus a lower contact area for the gear teeth - as the teeth are further apart and not correctly meshed hence the whine
Now we didn't have all the fancy tools you need to put the shim beneath the bearing seat, so we pulled the bearing off the shaft itself, and had a shim machined to suit - put it all back together and it was lovely!
Not rocket science, but a right prat about - even on the bench!
Mike
Britannica Restorations Ltd
Canada