You will probably find the time on ACL4.3 is faster, but looking at
your lisp code I could not find the benchmark that you
actually ran for the times.  Also, setting the compiler
optimization to  (speed 3)(debug 0) may speed it up if you
have not done so already.
  Before spending much time on speeding up code, I recommend
strongly that you profile it to see where time is being spent.
RJF