Good point. Though potentially you could get some sort of gps type gadget to act as an odometer. On my Carlton that the speedo wasn't working on, it was only a temporary thing - my mate that I bought it off had put a new clutch in and not properly reconnected the speedo cable - no big deal - I lived with it for a bit and when I got around to it it literally took a minute or so to fix. I assume doing a straight swap with a good whole instrument panel is too much hassle, is it?
Yup, know what you mean - combined with the other unknowns, it's where you start to think "f*ck it" and get rid of the thing.
Ah yes - that's a 'drop test' isn't it? Much better to do some proper tests than go all gung-ho doing unneccessary work.