Another job whilst all the bodywork was happening was refurbishment and replacement of the various parts of the drivetrain.
Gearbox and Overdrive - After some research, I decided that Overdrive Repair Services in Sheffield (https://www.overdrive-repairs.co.uk/) seemed to be the place to send both gearbox and overdrive for refurbishment. They were very friendly and accommodating and returned the refurbished items within two weeks as I was on quite a tight deadline. If you can strap the unit securely to a pallet, they can arrange for their couriers to collect and return once the work has been completed. The other option of course is to take the units up there yourself and pick them back up again if you're worried about damage during transit, but fortunately I didn't have any issues when I shipped them.
Thrust Washers – Anyone who knows anything about a '6' knows that this can be one of its 'Achilles Heels'. Needless to say that I had uprated replacements fitted whilst Overdrive Repairs were doing the gearbox and overdrive.
Additionally, I fitted a new replacement speedo drive from Speedograph Richfield (http://www.speedograph-richfield.com/)... expensive, but beautiful engineering and worth the extra money.
I was hoping that having gone to all the effort of rebuilding the gearbox, all the oil leaks that I previously had would be resolved and I'd have a nice clean garage floor… I can but dream I guess… she still leaks sadly.. nowhere near as badly as before… but I still find the odd few drips on the floor. So if anyone knows how to fix the leaks permanently, I'm all ears.
Clutch - I had the old clutch, which was a Borg & Beck unit from a few years ago. It worked fine, but general consensus seemed to be that if you could get hold of an original Laycock plate, cover and bearing, that would be the best way to go. So, after some hunting around, I managed to acquire a new original stock set from the TR Shop in Chiswick (https://www.trshop.co.uk/). I also replaced the clutch master cylinder (there are two bore sizes for these it seems) and slave cylinder, the latter with a unit from a Triumph GT6 as I'm informed that this makes the clutch smoother and less 'stiff'. I don't know whether this is true or not, but I'm certainly happy with the operation of the clutch now.
Prop Shaft - This was rebuilt by Propshaft Services in Feltham (http://www.propshaft-services.co.uk/). The work took a few days and I had the Universal Joints uprated and the propshaft balanced whilst it was there.
Differential - Glen took the back off the diff and had a good look around to make sure it was sound. The crown wheel and pinion, and all the gearing looked good. It was working fine and noise-free before the car went in for rebuild so there was no reason to assume that this wouldn't be the case on the rebuilt car. Of course… 200 miles into the running-in process, the pinion bearing gives up the ghost! Moral of story… I should have just had it done at rebuild stage whether it looked like it needed doing or not… it went to Hardy Engineering in Leatherhead (https://www.hardyengineering.co.uk/) to be rebuilt. Bill at Hardy was really friendly and explained the process of what did, and didn't need doing, and the rebuilt diff was back in about a week or so.
Driveshafts - There's much discussion on whether to keep the standard driveshafts with uprated universal joints, or go with CV driveshafts. You will find many more people saying stick with the standard set up than go for CV driveshafts, so, if you want to play it safe, then it looks like the wise money would go on the original UJ set up. However, I'm not usually one for 'playing it safe', and this car was never going to be a standard TR6, so I've opted for the CV driveshafts from Classical Driving Development (https://www.classicdrivingdevelopment.co.uk/). They are beautifully engineered, and certainly look well made… only time will tell I guess whether I have made the right decision or not.