Just very belatedly seen this. I'm no device driver expert but in some circumstances it clearly is possible.
I have a Minolta film scanner for which there is no 64 bit driver, and it's an expensive piece of kit. I found the following page:
which basically says: install old driver, then update with new INF file.
To my surprise it worked perfectly - and the .SYS files had all come from the old 32 bit XP installer.
So, yes, sometimes you can, and it probably all depends what those .SYS files get up to and how they were written. Exactly what you need to do to convert the old .INF file to the new is complex - fortunately he provided one in this case. If one diffs the files they are not similar at all.