I spent many years wondering why my 410 was showing so many rpm for a given mph but I learnt a salutary lesson "use your head and do not necessarily trust the instruments" when the petrol gauge sender failed. The car started running out of petrol while the gauge said full (NB the quick acting moving coil gauges that Bristols used fail to full), my brain trusted the guage and started to create all sorts of reasons for fuel not getting to the right place, but it never dawned on me that the problem was actually the guage. To confound the issue the reserve switch had also decided to give up simultaneously - gremlins work in pairs. I was rescued quite quickly by an amused RAC man who went back to first principles and insisted on adding petrol. Worked like a charm.
Emboldened by this knowledge, i.e. it is at least as likely (or perhaps more likely if Lucas were involved) that the guage is at fault I researched the Rev counter to find that over reading is a common problem. So off it went to be fixed and recalibatred. Yes, it was over reading by a considerable factor and now I drive along happily at 70 mph doing just as few actual rpm as before, but, as the counter isn't raising my blood pressure by lying to me, it is astonishing how much more relaxed the car feels.
My advice is to check the Rev counter first and foremost. I used
Home page, my only connection is as a satisfied customer.
By the way checking the number of up shifts from a gentle standing start should be easy? Also I am not aware that the 410 ever had any form of rev limiter. Cutting out at an indicated 5000 rpm sounds like another gremlin trying to distract you