Batboard

I have several Advisor pagers that I am wanting to use on the amateur radio band. They have the 450-465MHz (NRE6552C) boards in them. Would it be possible to move this down to the upper edge of the 70cm band? I assume this would require a re-tune of the Helical Filter, but I cannot find any information on how that is done. I also assume that most of the fixed component values probably wont need changed.

Has anyone done this before?

Or, does anyone know of a source for the 435-450MHz (NRE6551C) boards, or any boards that work in any amateur band for these pagers?