I like the 683 too. If for nothing more than the CCP module. Of course the extra RAM and program space is also handy.

With the 629 only having 64 bytes of RAM,
PBP uses 24-26 bytes
and DT_INTS-14 and ReEnterPBP want 31 bytes of it (without T? vars)

Which only leaves about 6-7 bytes for the program. Not much you can do with that.

But, when using ASM interrupt handlers, DT_INTS-14 only needs 7 bytes of RAM, leaving around 38 bytes for the users program. Now that, is workable. It also uses less program space that way.

You mentioned earlier that you only needed to toggle a pin in the interrupt, so you might take a look at this page...

DT_INTS-14 (Assembly Language Interrupts)
http://www.darreltaylor.com/DT_INTS-14/asm_ints.html

The ToggleLED1: handler does just that. And if the other handlers aren't too tuff, you might still fit it in a 629.

HTH,
  DT