Thoughts on values of chameleons

[Hair Bear]

Hi, I'm sort of in the market for a 550 or a 20D, and wondering about the apparent growing fashion for model changing.
I've had dealings with curious coloured Masseys in the past, notably a 203 and a couple of 35s all of which had been fully painted in Ford blue probably from new - no idea why - point being regardless of red, yellow, or blue(!), they were still a 203 or a 35.
Anyhow on the 550 hunt I found two in the space of three days. First was a yellow one, obviously was red/grey originally, and had been industrialised early in it's life but definitely a 550. Now the next one I find is red/grey that had been yellow. Seller says it's definitely a 550 so I arranged to view. It's got 550 on the bonnet, but has a speedo pod on the dash and the cab plate clearly showing MF 20D. There are also several YT films showing 'restorations' of a 20D into a 550.
How would any of you value a 20D to a 550 or a converted 20D compared to a genuine 550? I'm not averse to a converted / colour changed one but I feel the asking price should reflect any lack of originality.
Thoughts?