I thinking of fitting a overdrive into the LT95 gearbox, but I see there is a fitting kit you need. Snap rings, shims & thrust washers.
Does anybody know who supplies this kit along with new internal bearings?

No replies - not a good omen
Nobody got an old LT95 gearbox with overdrive fitted?

Hi Mate, Try this....
John Craddock LTD

and this as a guide, it shows a series overdrive but the Rangerover overdrive is similar:
Fairey Overdrive Overhaul ? Nick's Land Rover - Series III rebuild and restoration

fitting a series overdrive, again very similar approach.
Fitting a Fairey Overdrive to a Series 3 Land Rover

Word of warning....
Before you do anything
Make sure it's in 3rd gear as you fit it or a thrust washer may drop off a step and you'll lose 2nd gear. Use a bungie on the gearstick to make sure it doesn't pop out.
If the shaft moves forward you will have hell on to get it back in position!!!!!
Good Luck.

I run one, make sure you change all the so called oil seals which are just O rings otherwise it will leak live a sieve- normally back in the t-case which overfills it and then it leakes everywhere too lol.