and, sorted by Performance Index ...

 Bus Type                              Performance Index    RPM @ 60 mph
 1.6 Vanagon Diesel Westy <extra 175 kg>    46.7                3650
 1.6 Vanagon Diesel                         52.3                3650
 1600 'loaf Westfalia  <extra 140 kg>       56.4                3484
 2000 Vanagon Westy <extra 175 kg>          59.4                3072
 1500 Micro Westfalia  <extra 130 kg>       59.7                3575
 1600 Breadloaf                             62.7                3484
 1700 'loaf Westfalia  <extra 140 kg>       64.1                3484
 2000 'loaf Westfalia  <extra 160 kg>       64.4                3181
 1200 Micro                                 64.5                3719
 1800 'loaf Westfalia  <extra 160 kg>       65.0                3416
 2000 Vanagon                               66.9                3072
 1500 Micro <gearing for 1 ton GCW>         67.0                3575
 1.9 Vanagon Westy <extra 175 kg>           70.3                3267
 1700 'loaf                                 70.9                3484
 2000 'loaf                                 72.2                3181
 2.1 Vanagon Westy <extra 175 kg>           72.3                3072
 1800 'loaf                                 72.9                3416
 1.9 Vanagon Wasserboxer                    79.1                3267
 2.1 Vanagon                                81.4                3072

so it would appear that the Index does mimic real life:
  the diesels are the slowest, and the gasoline-powered Vanagons are the
  "quickest". :)

but, Dave, where are the Eurovans ... ??? :)

joel