Its always been said that most oil is drawn in through valve guides on overrun. That is drive, throttle off and then accelerate which, if a puff of smoke is produced, indicates worn valve guides ..
Are you having problems with the dynamo then Martyn? Ive still got mine (25amp max) and it supplies all I need ok but then theres no extra load apart from an electric fan...
One problem I can see straight away is that the splines are different. For cost savings Triumph later went to rolled fine splines for many drives (gearbox, clutch and diff) in place of machined ones. This means you would need the later coupling however I have a feeling theres other issues as well....
The carcass was supposed to be closely inspected before reuse in remolds. Must admit I never had any problems with them but the new tread never lasted as long as the original. I always assumed a softer, lower temperature compound was used so as not to damage that of the original carcass...
You should have used 'Blakeys' shoe protectors to avoid R-Soles😁 Wow I see theyre still available...
BLAKEY'S SEGS – The Original Shoe Protectors (blakeys-segs.co.uk)
As your brakes have never been good I think I would install Mintex pads first before stripping anything. Some pads can be absolutely awful (see previous posts on here) and anyway the Mintex are likely to be better than whatever youve already got but if still lacking then inspect further.....
The expensive ones like this come in a huge range of diameters and grip girth with the price going up a lot the bigger the size...
PERF. LEATHER STEERING WHEEL COVER FOR TRIUMPH VITESSE BLACK SEAM | eBay
Hmmm wonder if the pads are fully bedded in as this can take a few miles. Saying that cheap aftermarket pads can be pretty awful and as reported many times on here a change to Mintex 1144 (the label must actually say that) or NOS asbestos pads makes for a big improvement....
But the pads used to brake ok didnt they? If so are they still in good condition? Were you overheating the brakes on steep curvy downhills? Also have you got a servo fitted?
Brilliant and the operator now makes good contact with the ball? I think this is important so that if the switch 'relaxes' a bit with usage (like the old one?) theres still enough to ensure continued correct operation...
As Pete says discount all external possibilities first perhaps even getting the car securely up on axles stands and running it in first and reverse to try to locate the noise. However in the gearbox 1st and reverse gears are physically in close proximity so there could be something going on between the various components...