I
noticed the something when I switched a bug engine into a 71. Nobody seemed t
o think there was a problem but the space was still there, and BTW I did burn
out an engine in that 71 (though it may be unrelated). Some points to
consider:
  the 71 is the last upright oriented bus (and you could say the best), it is
the only one that has the throttle tube hole just like it does. I wonder if it
my be the 71? My 69 doesn't have the same amount of space. I will know more
about it when I pull it in a couple of days.

                                         Tim