32-bit integers

I have implemented the Blowfish encryption algorithm in lisp and
would like to optimize its speed. Currently I have straightforwardly 
implemented the algorithm as described by its inventor 
(see http://www.counterpane.com/blowfish.html) which means it's using
bignums to represent 32 bit integers. For my current purposes, this
is more than fast enough, but if I later decide to use this code to 
encrypt significant amounts of data, it's not good enough.

So:
 - Is there a way to use unboxed 32bit (unsigned) integers in LW?
 - if not, when can we get it ;-)?

(Btw, I implemented 32 bit arithmetic through pairs of 16-bit halves
 and discovered that there actually is something very similar to my
 code in the memory-manager package, but I couldn't find any
 documentation)
-- 
  (espen)