I've done a number of EFI conversions into older cars, and actually spent this afternoon stripping and modifying an MGF loom for the TR7 upgrades. But these are discrete and simple systems because they're nearly thirty years old. More modern ones that are fully integrated with each other are far more complex to work with, and really don't like somebody with a loom spread over the garden chopping out things like the airbags, ABS and air conditioning with some sidecutters. I doubt I'd consider doing the same job with a Rover 75

. Then there's the parts availability - just how are you going to fix a 4l30E solenoid fault, worn gear selector switch, failed MAF or dead crank sensor when there are
none available? Mechanical parts can still be cobbled together in a shed, I'd be amazed if anyone is going to bother doing that for those parts that are going to be one-offs unless they
really want the car again.
Triumph's PI is a typical example of them half-arsing things, as it's barely any different from Bosch's contemporary systems. Except they provided a proper fuel pump which actually does the job. Plenty of people blame the bit they are afraid of for not being able to fix a problem. Before injection became common, carburettors got the blame for all sorts of problems that were nothing to do with them.
It seems that we are on the same page with valuations: they're for those who have managed to get an agreed value insurance policy. As a way of stitching up insurance companies whose SOP(the principle of car insurance is that you pay them a hefty chunk of cash, and they send you a piece of paper) is to do that to their customers, I'm for it. But clubs delight in telling their members how they 'got a bargain' and then offer howls of derision when the club's own valuation is suggested for a selling price.
Dramatically rising values can be detrimental for a lot of enthusiasts too. The result of a sudden large increase in value, often means would be owners can no longer afford what they were intending to buy. I see that with Capris; I'd love to replicate my 2.0Si as an everyday car, but it's probably a £10k build not the <£1000 the original one was. It simply isn't worth that to me now, even if I had the cash. That grand included buying the car, as well as all the modifications.