"We have many noise issues reported on R380’s when fitted to the TD5 engines when a single mass flywheel is used instead of the stock duel mass type, the single mass flywheels make the gearboxes ‘chatter’ badly on idle and when not under load, this does not appear to be detrimental to the gearbox but does not sound good at all, we do not treat this as a gearbox fault, its caused by the single mass flywheel transferring the knock of the diesel engine to the gearbox and making the gearbox rattle."
This is a direct quote from Ashcroft Transmissions. If a gearbox specialist of over 40 years states this, I'd believe them.
Whilst maybe not detrimental to the gearbox, it would be for the driving experience imo, you can read countless experiences of people running standard clutchees with fairly hefty tunes and doing thousands upon thousands of miles.
A chap I work for has a very strong map and is on 211000k on original clutch,, he tows a trailer everyday but drives it how you are supposed to drive a defender. Non of this revving up dropping the clutch crap.
I'd personally say stick with original turbo ( although driven sympathetically I'd question having to switch to single mass anyway) , but depends what you want/ need from your vehicle.
I've built my defender to run everyday with a trailer, through forestry and all sorts. Mine runs quite a good map and on 160k the clutch hasn't been touched and is showing no signs of needing to!