"16 Bit Architecture in 40 Pin DIP"

If you are willing to use PLCC44 (with a converter socket if you must) There is the wunnerful Philips XA series. Siemens has the 167 and 168 series and intel has the 251 series. All the above are 'next generation '51 chips with many familiar features and some new stuff. Some are 8 bit external - 16 bit internal, The XA can be configures as 8 or 16 bit external and is 16 bit internal.

Have fun,

Erik