From memory, the pre 1957 UK rules did allow a certain amount of modification but apart from a limitation on carb size increases, wider steel wheels etc., I seem to remember springs were free (hence the two wheeling A35s) but it was a case of decent handling rather than huge horsepower.

I can admire a static car that has beauty - 250F Maserati, P25 BRM, V12 Eagle, 212 Aston - and any number of exotics, but the run of the mill does needing firing up to be of interest. The festival will of course say the cars are the stars, but as a visit to the Goodwood Festival usually proves, many static cars are indeed the stars, whereas a modern wailing screeching advertising bedecked F1 car or Aussie V8 taxi is not a star.