Thinking about this ten million credits in the test track accolade, I thought it might be worth having a look at which cars could be more likely to have the most expensive options for upgrading.
To do that the only vaguely sensible way to look of which I could think was ordering my cars by PI (they’re all stock) and then seeing what the auto-upgrade menu had in it. Of course, that’s not going to be anywhere near thorough but there might be some correlation. The time taken to look in detail is not worth the effort. Not even sure doing what I did was worth the effort either!
For D class most of them can be auto-upgraded to A class.
S1 class - Toyota AT38.
B class - Bentley Blower, Ford Transit SSV, Ford F-150 '86, Ford Anglia '59, Ford F-100, Ford Wagon, Ford Coupe '40, Ford Coupe '32, LR Defender, Range Rover '73, M-B Unimog, M-b SSK, Morgan 3 Wheeler, Morris Traveler, Nissan Safari, Reliant Supervan, Renault 4L '68, Toyota FJ40, VW Class 5 Bug, VW Beetle, VW Type 2, Willys Jeep, Wuling Sunshine.
C class - Bentley 8 Litre, Ford Transit Mk1, LR Series III, VW Pickup '82.
Still D class - BMW Isetta, Peel Trident, Peel P-50,
The issues now are (1) is that actually of any use to anyone anywhere and (2) can I really be bothered to keep going?